Guidance for using pilot studies to inform the design of intervention trials with continuous outcomes

Bell, Melanie L; Whitehead, Amy L; Julious, Steven A

doi:10.2147/clep.s146397

Cited by 280Statistical Methods in Clinical TrialsStatistical Methods in EpidemiologyMeta-analysis and systematic reviews

Guidance for using pilot studies to inform the design of intervention trials with continuous outcomes

Open access

Bell, Melanie L, Whitehead, Amy L, Julious, Steven A·2018·Clinical Epidemiology

DOI 10.2147/clep.s146397PMC PMC5779280

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Abstract

BACKGROUND: A pilot study can be an important step in the assessment of an intervention by providing information to design the future definitive trial. Pilot studies can be used to estimate the recruitment and retention rates and population variance and to provide preliminary evidence of efficacy potential. However, estimation is poor because pilot studies are small, so sensitivity analyses for the main trial's sample size calculations should be undertaken. METHODS: We demonstrate how to carry out easy-to-perform sensitivity analysis for designing trials based on pilot data using an example. Furthermore, we introduce rules of thumb for the size of the pilot study so that the overall sample size, for both pilot and main trials, is minimized. RESULTS: The example illustrates how sample size estimates for the main trial can alter dramatically by plausibly varying assumptions. Required sample size for 90% power varied from 392 to 692 depending on assumptions. Some scenarios were not feasible based on the pilot study recruitment and retention rates. CONCLUSION: Pilot studies can be used to help design the main trial, but caution should be exercised. We recommend the use of sensitivity analyses to assess the robustness of the design assumptions for a main trial.

AI snapshot

Written from the paper’s full text.

TL;DR

Pilot studies can inform the design of definitive trials with continuous outcomes by estimating recruitment/retention, population variance, and preliminary efficacy potential, but their small size makes estimates imprecise. The paper recommends sensitivity analyses and stepped rules of thumb for pilot sample size, illustrated by an example where required main-trial sample size for 90% power ranged from 392 to 692 depending on assumptions.

Key findings

In the worked example, main-trial sample size for 90% power varied from 392 to 692 depending on assumptions about the SD and dropout rate; for 80% power, sample sizes ranged from 296 to 518.
The pilot example had a recruitment rate of 50% of eligible patients, at 25 recruitments per month, and 80% retention (40 of 50 participants completed all three assessments).
Based on a target standardized effect size of 4/14 = 0.29 for a 90% powered main trial, the stepped rules of thumb indicated 25 patients per arm for the pilot.
Feasibility assessment showed that recruiting over 1.5 years at 25 participants per month would enroll 450 participants, falling below several sample size estimates in the sensitivity analysis.

Methods

Methodological guidance paper with a worked example using a continuous outcome; it focuses on external pilot studies whose results are not combined with the main trial.
The example is a hypothetical two-arm RCT comparing a new supportive care regimen for cancer patients to usual care, with quality of life at 3 months measured by FACT-G; the pilot had 50 participants, with 100 potential participants, 70 referred, 60 eligible, and 50 agreeing to participate.
Main analysis demonstrates sample size sensitivity analyses varying the SD (pilot SD, upper 80% CI limit, literature estimate) and dropout rates (observed 20%, >5%, <5%), plus stepped rules of thumb for pilot sample size based on target effect size and future trial size.

Limitations

Stated: pilot studies are small, so effect size and SD estimates are imprecise; using a pilot study’s SD to design a future sample size has been shown to often result in an underpowered study, and preliminary efficacy evidence from a pilot should not be overstated.
Stated: sensitivity analyses are needed because sample size estimates can alter dramatically by plausibly varying assumptions, and some scenarios may not be feasible based on pilot recruitment and retention rates.
Evident from the text: the worked example is explicitly hypothetical (“Suppose…”), so its numerical results are illustrative rather than empirical findings from an actual pilot study.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.2147/clep.s146397

Cites

32 of 32 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 45 cited sources checked · 0 supported · 0 flagged

Findingown data
Required sample size for 90% power varied from 392 to 692 depending on assumptions.
“Required sample size for 90% power varied from 392 to 692 depending on assumptions.”
- Also stated in: § Sample size calculations and sensitivity analyses · plain
  “For 90% power, sample size ranges from 392 to 692.”
Quote in the paperSubstantial claim
Findingown data
The example illustrates how sample size estimates for the main trial can alter dramatically by plausibly varying assumptions.
“The example illustrates how sample size estimates for the main trial can alter dramatically by plausibly varying assumptions.”
- Also stated in: § Conclusion · boosted
  “The example demonstrated how main trial sample size estimates can vary dramatically by plausibly altering assumptions.”
Quote in the paperSubstantial claim
Findingown data
Some scenarios were not feasible based on the pilot study recruitment and retention rates.
“Some scenarios were not feasible based on the pilot study recruitment and retention rates.”
Quote in the paperNot a substantial claim
Findingown data
For 80% power, sample sizes range from 296 to 518.
“For 80% power, sample sizes range from 296 to 518.”
Quote in the paperNot a substantial claim
Findingreasoning
Using an MID estimate of four points and an SD of 14, the standardized effect size is 4/14=0.29.
“Using an MID estimate of four points, and an SD of 14, the standardized effect size is 4/14=0.29.”
Quote in the paperSubstantial claim

Findingown data
Each CI contains the MID of 4.
“Figure 1 shows several CIs demonstrating that the intervention is promising, as each CI contains the MID of 4.”
Quote in the paperSubstantial claim
Premisecitation
The estimated effect size and confidence interval from the pilot can give some evidence whether there is any indication that the intervention is effective and important differences might be obtained in the main trial.
“The target effect size must also be realistic, and the estimated effect size and confidence interval (CI) from the pilot can give some evidence here, ie, whether there is any indication that the intervention is effective and important differences might be obtained in the main trial.5”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [5] Cocks K Torgerson DJ Sample size calculations for pilot randomized trials: a confidence interval approach J Clin Epidemiol 2013 66 2 197 201 23195919
  Not checked in the free run.
Premisecitation
Estimation from pilot studies is poor because pilot studies are small.
“However, estimation is poor because pilot studies are small, so sensitivity analyses for the main trial’s sample size calculations should be undertaken.”
- Also stated in: § Target effect size and potential efficacy · plain
  “The small sample size of a pilot makes estimation uncertain, so caution must be exercised.19,20”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites [19] Kraemer HC Mintz J Noda A Tinklenberg J Yesavage JA Caution regarding the use of pilot studies to guide power calculations for study proposals Arch Gen Psychiatry 2006 63 5 484 489 16651505
  Not checked in the free run.
- cites [20] Loscalzo J Pilot trials in clinical research: of what value are they? Circulation 2009 119 13 1694 1696 19349331
  Not checked in the free run.
Premisecitation
The small sample size of a pilot makes estimation uncertain.
“The small sample size of a pilot makes estimation uncertain, so caution must be exercised.19,20”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites [19] Kraemer HC Mintz J Noda A Tinklenberg J Yesavage JA Caution regarding the use of pilot studies to guide power calculations for study proposals Arch Gen Psychiatry 2006 63 5 484 489 16651505
  Not checked in the free run.
- cites [20] Loscalzo J Pilot trials in clinical research: of what value are they? Circulation 2009 119 13 1694 1696 19349331
  Not checked in the free run.
Premisecitation
Pilot studies can give estimates of retention rates and adherence rates.
“pilot studies can also give estimates of retention rates and adherence rates.11”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [11] Avery KNL Williamson PR Gamble C Informing efficient randomised controlled trials: exploration of challenges in developing progression criteria for internal pilot studies BMJ Open 2017 7 2 e013537 PMC5318608 28213598
  Not checked in the free run.
Premisereasoning
The SD can be imprecisely estimated due to the pilot's small sample size.
“However, similar to the effect size, the SD can be imprecisely estimated due to the pilot’s small sample size.”
Quote in the paperSubstantial claim
Interpretationreasoning
Pilot studies can be used to help design the main trial.
“Pilot studies can be used to help design the main trial, but caution should be exercised.”
- Also stated in: § Conclusion · boosted
  “We have illustrated how pilot studies can aid in the design of future trials with continuous outcomes by providing estimates of population SD, evidence of potential for intervention effectiveness, and quantification of feasibility in the form of recruitment and retention rates.”
Quote in the paperSubstantial claim
Premisecitation
Missing data and dropouts are issues in most RCTs.
“Missing data and dropouts are issues in most RCTs12 and need to be considered at each step of the research process,13 including design, reporting,9 and progression to a larger definitive trial.11,14”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [12] Bell ML Fiero M Horton NJ Hsu CH Handling missing data in RCTs; a review of the top medical journals BMC Med Res Methodol 2014 14 1 118 25407057 PMC4247714
  Not checked in the free run.
Premisecitation
Using a pilot study's SD to design a future sample size has been shown to often result in an underpowered study.
“Using a pilot study’s SD to design a future sample size has been shown to often result in an underpowered study.23,24”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites [23] Browne RH On the use of a pilot sample for sample size determination Stat Med 1995 14 17 1933 1940 8532986
  Not checked in the free run.
- cites [24] Vickers AJ Underpowering in randomized trials reporting a sample size calculation J Clin Epidemiol 2003 56 8 717 720 12954462
  Not checked in the free run.
Premisecitation
Pilot studies provide estimates of the number of participants that actually enroll and consent to randomization.
“pilot studies provide estimates of the number of participants that actually enroll and consent to randomization, and these estimates should be included in the manuscripts that report the pilot study results.9”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [9] Eldridge SM Chan CL Campbell MJ CONSORT 2010 statement: extension to randomised pilot and feasibility trials BMJ 2016 355 i5239 27777223 PMC5076380
  Not checked in the free run.
Premisecitation
Failure to recruit is a major issue in UK publicly funded trials, where 45% fail to reach target sample size.
“Failure to recruit is a major issue in UK publicly funded trials, where 45% fail to reach target sample size.10”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [10] Sully B Julious SA Nicholl J A reinvestigation of recruitment to randomised, controlled, multicenter trials: a review of trials funded by two UK funding agencies Trials 2013 14 166 23758961 PMC3691846
  Not checked in the free run.
Interpretationreasoning
The intervention is promising.
“Figure 1 shows several CIs demonstrating that the intervention is promising, as each CI contains the MID of 4.”
Quote in the paperSubstantial claim
Premisecitation
Using these rules increases the likelihood of appropriate power for the future trial.
“Using these rules increases the likelihood of appropriate power for the future trial.”
Quote in the paperSubstantial claim
Premisecitation
Whitehead et al. showed how, if you know the main trial's target effect size, you can estimate the pilot study's optimum sample size, minimizing the number of patients recruited across the two studies.
“Whitehead et al27 showed how, if you know the main trial’s target effect size, you can estimate the pilot study’s optimum sample size, minimizing the number of patients recruited across the two studies.”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [27] Whitehead A Julious S Cooper C Campbell MJ Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable Stat Methods Med Res 2016 25 3 1057 1073 26092476 PMC4876429
  Not checked in the free run.

Classified as probably not a substantial claim. 23
May combine two claims. 15

Probably not a substantial claim: may not pass S3 (load-bearing).
Findingreasoning
If the pilot recruitment rate of 25 participants per month is a good estimate, then the study will be able to recruit and enroll 450 participants.
“If the pilot recruitment rate of 25 participants per month is a good estimate, then the study will be able to recruit and enroll 450 participants.”
Quote in the paperNot a substantial claim
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Findingown data
Of the 50 participants, 40 completed all three assessments; retention is 80%.
“Of the 50 participants, 40 participants completed all three assessments; retention is 80%.”
Quote in the paperNot a substantial claim
May combine two claims.
Findingreasoning
The pilot study of 50 participants had a recruitment rate of 50% of eligible patients, at 25 recruitments per month.
“This indicates a recruitment rate of 50% of eligible patients, at 25 recruitments per month.”
Quote in the paperNot a substantial claim
May combine two claims.
Findingnone given
The difference in quality of life between the arms at 3 months is estimated at 3.1 points, with 95% CI −1.8 to 8.0, and SD =11.2.
“The difference in the quality of life between the arms at 3 months is estimated at 3.1 points, with 95% CI −1.8 to 8.0, and SD =11.2.”
Quote in the paperSubstantial claim
Probably not a substantial claim: may not pass S3 (load-bearing).
Findingown data
450 participants falls below several of the estimates in Table 2.
“This falls below several of the estimates in Table 2.”
Quote in the paperNot a substantial claim
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Premisecitation
Hislop et al. identified seven approaches for determining the target effect size for an RCT and classified them as clinically important and/or realistic.
“Hislop et al15 undertook a systematic review to identify seven approaches for determining the target effect size for an RCT and classified them as clinically important and/or realistic.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [15] Hislop J Adewuyi TE Vale LD Methods for specifying the target difference in a randomised controlled trial: the Difference ELicitation in TriAls (DELTA) systematic review PLoS Med 2014 11 5 e1001645 24824338 PMC4019477
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
Most pilot studies do undertake hypothesis tests.
“While some authors argue against carrying out hypothesis tests and assessing efficacy from pilots, even potential efficacy, most pilot studies do undertake hypothesis tests.6”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [6] Shanyinde M Pickering RM Weatherall M Questions asked and answered in pilot and feasibility randomized controlled trials BMC Med Res Methodol 2011 11 1 117 21846349 PMC3170294
  Not checked in the free run.
May combine two claims.
Premisecitation
Pilot studies can be used to estimate recruitment and retention rates and population variance and to provide preliminary evidence of efficacy potential.
“Pilot studies can be used to estimate the recruitment and retention rates and population variance and to provide preliminary evidence of efficacy potential.”
- Also stated in: § Introduction · plain
  “To address this aim, there are a number of objectives for a pilot study including assessing recruitment and retention rates, obtaining estimates of parameters required for sample size calculation, and providing preliminary evidence of efficacy potential.3–6”
Quote in the paperSubstantial claim0 of 4 sources checked
- cites [3] Craig P Dieppe P Macintyre S Developing and evaluating complex interventions: the new Medical Research Council guidance BMJ 2008 337 a1655 18824488 PMC2769032
  Not checked in the free run.
- cites [4] Lancaster G Campbell M Eldridge S Trials in primary care: statistical issues in the design, conduct and evaluation of complex interventions Stat Methods Med Res 2010 19 4 349 377 20442193
  Not checked in the free run.
- cites [5] Cocks K Torgerson DJ Sample size calculations for pilot randomized trials: a confidence interval approach J Clin Epidemiol 2013 66 2 197 201 23195919
  Not checked in the free run.
- cites [6] Shanyinde M Pickering RM Weatherall M Questions asked and answered in pilot and feasibility randomized controlled trials BMC Med Res Methodol 2011 11 1 117 21846349 PMC3170294
  Not checked in the free run.
Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).
Premisecitation
A figure showing CIs, the MID, and the null value can be a helpful way of displaying pilot results.
“A figure showing these CIs, the MID, and the null value can be a helpful way of displaying pilot results, by facilitating an assessment of both statistical significance and the potential for clinical significance.31”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [31] Bell ML Fiero MH Dhillon HM Bray VJ Vardy JL Statistical controversies in cancer research: using standardized effect size graphs to enhance interpretability of cancer-related clinical trials with patient-reported outcomes Ann Oncol 2017 28 8 1730 1733 28327975 PMC5834129
  Not checked in the free run.
Classified as probably not a substantial claim. May combine two claims.
Premisenone given
Pilot trial results can inform target effect size, variance, and feasibility.
“Pilot trial results can inform each of these elements.”
Quote in the paperSubstantial claim
May combine two claims.
Premisenone given
The population SD is a key element of sample size estimation for continuous outcomes, and its estimation is one of the objectives for conducting a pilot study.
“The population SD is another key element of sample size estimation for continuous outcomes, and its estimation is one of the objectives for conducting a pilot study.”
Quote in the paperSubstantial claim
Classified as probably not a substantial claim.
Premisecitation
In the absence of a known MID for continuous outcomes, particularly patient-reported outcomes, a standardized effect size between 0.3 and 0.5 has been recommended.
“In the absence of a known MID for continuous outcomes, particularly patient-reported outcomes, a standardized effect size15 between 0.3 and 0.5 has been recommended.17,18”
Quote in the paperSubstantial claim0 of 3 sources checked
- cites [15] Hislop J Adewuyi TE Vale LD Methods for specifying the target difference in a randomised controlled trial: the Difference ELicitation in TriAls (DELTA) systematic review PLoS Med 2014 11 5 e1001645 24824338 PMC4019477
  Not checked in the free run.
- cites [17] King M A point of minimal important difference (MID): a critique of terminology and methods Expert Rev Pharmacoecon Outcomes Res 2011 11 2 171 184 21476819
  Not checked in the free run.
- cites [18] Norman GR Sloan JA Wyrwich KW The truly remarkable universality of half a standard deviation: confirmation through another look Expert Rev Pharmacoecon Outcomes Res 2004 4 5 581 585 19807551
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
Type I error and power are set independent of the pilot.
“Factors such as type I error and power are set independent of the pilot and are discussed in detail elsewhere.7”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [7] Julious SA Sample sizes for clinical trials with normal data Stat Med 2004 23 12 1921 1986 15195324
  Not checked in the free run.
May combine two claims.
Premisecitation
Many trials struggle to reach their sample size goal, which can result in trial extensions or failure to recruit to their prespecified sample size.
“Many trials struggle to reach their sample size goal, which can result in trial extensions or failure to recruit to their prespecified sample size.10”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [10] Sully B Julious SA Nicholl J A reinvestigation of recruitment to randomised, controlled, multicenter trials: a review of trials funded by two UK funding agencies Trials 2013 14 166 23758961 PMC3691846
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Premisecitation
Pilot trials are often small versions of the main trial, undertaken to test trial methods and procedures.
“Pilot trials are often small versions of the main trial, undertaken to test trial methods and procedures.1,2”
Quote in the paperNot a substantial claim0 of 2 sources checked
- cites [1] Thabane L Ma J Chu R A tutorial on pilot studies: the what, why and how BMC Med Res Methodol 2010 10 1 20053272 PMC2824145
  Not checked in the free run.
- cites [2] Arain M Campbell MJ Cooper CL Lancaster GA What is a pilot or feasibility study? A review of current practice and editorial policy BMC Med Res Methodol 2010 10 67 20637084 PMC2912920
  Not checked in the free run.
Classified as probably not a substantial claim. May combine two claims.
Premisecitation
Objectives for a pilot study include assessing recruitment and retention rates, obtaining estimates of parameters required for sample size calculation, and providing preliminary evidence of efficacy potential.
“To address this aim, there are a number of objectives for a pilot study including assessing recruitment and retention rates, obtaining estimates of parameters required for sample size calculation, and providing preliminary evidence of efficacy potential.3–6”
Quote in the paperSubstantial claim0 of 4 sources checked
- cites [3] Craig P Dieppe P Macintyre S Developing and evaluating complex interventions: the new Medical Research Council guidance BMJ 2008 337 a1655 18824488 PMC2769032
  Not checked in the free run.
- cites [4] Lancaster G Campbell M Eldridge S Trials in primary care: statistical issues in the design, conduct and evaluation of complex interventions Stat Methods Med Res 2010 19 4 349 377 20442193
  Not checked in the free run.
- cites [5] Cocks K Torgerson DJ Sample size calculations for pilot randomized trials: a confidence interval approach J Clin Epidemiol 2013 66 2 197 201 23195919
  Not checked in the free run.
- cites [6] Shanyinde M Pickering RM Weatherall M Questions asked and answered in pilot and feasibility randomized controlled trials BMC Med Res Methodol 2011 11 1 117 21846349 PMC3170294
  Not checked in the free run.
May combine two claims.
Premisecitation
Using the pilot effect size to power the definitive trial is likely to mislead because estimation is poor due to the small sample size.
“Although some researchers use the pilot effect size to power the definitive trial, this is a practice that should be avoided in general, as estimation is poor due to the small sample size, and is likely to mislead.19”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [19] Kraemer HC Mintz J Noda A Tinklenberg J Yesavage JA Caution regarding the use of pilot studies to guide power calculations for study proposals Arch Gen Psychiatry 2006 63 5 484 489 16651505
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
Using significance levels other than the traditional 5% with corresponding CIs such as 85 and 75% in addition to 95% CIs can provide preliminary evidence for efficacy.
“One approach for handling this uncertainty is to use significance levels other than the “traditional” 5% to provide preliminary evidence for efficacy, with corresponding CIs such as 85 and 75% in addition to 95% CIs.21”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [21] Lee EC Whitehead AL Jacques RM Julious SA The statistical interpretation of pilot trials: should significance thresholds be reconsidered? BMC Med Res Methodol 2014 14 1 41 24650044 PMC3994566
  Not checked in the free run.
Classified as probably not a substantial claim.
Premisecitation
Whitehead et al. proposed stepped rules of thumb for pilot studies based on the target effect size and the size of the future trial.
“From this work, they proposed stepped rules of thumb for pilot studies based on the target effect size and the size of the future trial.”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [27] Whitehead A Julious S Cooper C Campbell MJ Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable Stat Methods Med Res 2016 25 3 1057 1073 26092476 PMC4876429
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
The decision to progress from a pilot trial to a main trial is generally made using feasibility estimates, as well as issues such as protocol nonadherence.
“The decision to progress from a pilot trial to a main trial is generally made using feasibility estimates, as well as issues such as protocol nonadherence.”
Quote in the paperNot a substantial claim0 of 2 sources checked
- cites [11] Avery KNL Williamson PR Gamble C Informing efficient randomised controlled trials: exploration of challenges in developing progression criteria for internal pilot studies BMJ Open 2017 7 2 e013537 PMC5318608 28213598
  Not checked in the free run.
- cites [14] Hampson LV Williamson PR Wilby MJ Jaki T A framework for prospectively defining progression rules for internal pilot studies monitoring recruitment Stat Methods Med Res Epub 2017 1 01 28589752
  Not checked in the free run.
May combine two claims.
Premisecitation
There are several rules of thumb for the size of a pilot study, ranging from 12 to 35 individuals per arm, and none of these guidelines account for the likely size of the future trial.
“While there are several rules of thumb for the size of a pilot study, ranging from 12 to 35 individuals per arm,5,27 none of these guidelines account for the likely size of the future trial.”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites [5] Cocks K Torgerson DJ Sample size calculations for pilot randomized trials: a confidence interval approach J Clin Epidemiol 2013 66 2 197 201 23195919
  Not checked in the free run.
- cites [27] Whitehead A Julious S Cooper C Campbell MJ Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable Stat Methods Med Res 2016 25 3 1057 1073 26092476 PMC4876429
  Not checked in the free run.
May combine two claims.
Premisereasoning
Traditional power calculations are inappropriate for pilot studies because the primary aim of a pilot study is not to test superiority of one treatment over the other.
“Although traditional power calculations are inappropriate for pilot studies (since the primary aim of a pilot study is not to test superiority of one treatment over the other), a sample size justification is important.”
Quote in the paperSubstantial claim
May combine two claims.
Interpretationreasoning
Pilot studies can aid in the design of future trials with continuous outcomes by providing estimates of population SD, evidence of potential for intervention effectiveness, and quantification of feasibility in the form of recruitment and retention rates.
“We have illustrated how pilot studies can aid in the design of future trials with continuous outcomes by providing estimates of population SD, evidence of potential for intervention effectiveness, and quantification of feasibility in the form of recruitment and retention rates.”
Quote in the paperSubstantial claim
Classified as probably not a substantial claim.
Interpretationown data
These rates will aid in estimating the main trial duration.
“These rates will aid in estimating the main trial duration.”
Quote in the paperSubstantial claim
May combine two claims.
Premisecitation
The estimated FACT-G MID is between three and six points and an SD estimate from the literature is 14 in similar populations.
“They find that the estimated FACT-G MID is between three and six points29 and an SD estimate from the literature30 is 14 in similar populations.”
Quote in the paperSubstantial claim0 of 2 sources checked
- cites [29] Webster K Cella D Yost K The functional assessment of chronic illness therapy (FACIT) measurement system: properties, applications, and interpretation Health Qual Life Outcomes 2003 1 79 14678568 PMC317391
  Not checked in the free run.
- cites [30] Bell ML McKenzie JE Designing psycho-oncology randomised trials and cluster randomised trials: variance components and intra-cluster correlation of commonly used psychosocial measures Psychooncology 2013 22 8 1738 1747 23080401
  Not checked in the free run.
Classified as probably not a substantial claim.
Premisecitation
Sensitivity analyses can take the form of accounting for the uncertainty in estimation by calculating sample sizes based on a range of plausible SDs and retention/dropout rates.
“Sensitivity analyses should also be performed in the design stage26 and can take the form of accounting for the uncertainty in estimation by calculating sample sizes based on a range of plausible SDs and retention/dropout rates.”
Quote in the paperSubstantial claim0 of 1 sources checked
- cites [26] Lewis JA Statistical principles for clinical trials (ICH E9): an introductory note on an international guideline Stat Med 1999 18 15 1903 1942 10440877
  Not checked in the free run.
Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).
Premisecitation
Sensitivity analyses are important to assess the robustness of study results to the assumptions made in the primary analysis.
“Sensitivity analyses are important to assess the robustness of study results to the assumptions made in the primary analysis.25”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [25] Thabane L Mbuagbaw L Zhang S A tutorial on sensitivity analyses in clinical trials: the what, why, when and how BMC Med Res Methodol 2013 13 1 92 23855337 PMC3720188
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Interpretationreasoning
The objective of the pilot study to provide preliminary evidence of efficacy has been met.
“Thus, the objective of the pilot study to provide preliminary evidence of efficacy has been met.”
Quote in the paperNot a substantial claim
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
For a future trial designed around a small effect, the number of patients per arm for the pilot study should be 25 for 90% power.
“For example, if the future trial will be designed around a small effect, then the number of patients per arm for the pilot study should be 25 for 90% power.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [27] Whitehead A Julious S Cooper C Campbell MJ Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable Stat Methods Med Res 2016 25 3 1057 1073 26092476 PMC4876429
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
A CONSORT extension for reporting results of pilot and feasibility studies gives detailed guidelines.
“A CONSORT extension for reporting results of pilot and feasibility studies gives detailed guidelines.9”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [9] Eldridge SM Chan CL Campbell MJ CONSORT 2010 statement: extension to randomised pilot and feasibility trials BMJ 2016 355 i5239 27777223 PMC5076380
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Interpretationreasoning
For a 90% powered main trial, they should use a sample size of 25 per arm for the pilot.
“For a 90% powered main trial, they should use a sample size of 25 per arm for the pilot (Table 1).”
Quote in the paperNot a substantial claim
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
Browne suggested using the pilot study's upper limit of the 80% CI for the SD to calculate sample size in the subsequent trial.
“Browne23 suggested using the pilot study’s upper limit of the 80% CI for the SD to calculate sample size in the subsequent trial.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [23] Browne RH On the use of a pilot sample for sample size determination Stat Med 1995 14 17 1933 1940 8532986
  Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Premisecitation
Cocks and Torgerson recommend basing the pilot study size on the future trial's size, if the SD is known.
“Cocks and Torgerson5 also recommend basing the pilot study size on the future trial’s size, if the SD is known.”
Quote in the paperNot a substantial claim0 of 1 sources checked
- cites [5] Cocks K Torgerson DJ Sample size calculations for pilot randomized trials: a confidence interval approach J Clin Epidemiol 2013 66 2 197 201 23195919
  Not checked in the free run.

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Each is checked against this paper’s own text: does it say what the citing paper says it does?

A sample size of 60 participants is adequate considering an effect size of 0.3 and 80% power.
“In order to stablish the sample size required for this trial, we follow recommendations by Bell et al. (2018) which proposed that a sample size of 60 participants would be adequate considering an effect size of 0.3 and 80% of power.”
From Unified Protocol for the transdiagnostic treatment of emotional disorders in people with post COVID-19 condition: study protocol for a multiple baseline n-of-1 trial (2023) · cites this paper as Bell et al., 2018
The ‘Target effect size and potential efficacy’ section says an effect size of 0.3–0.5 can be used when no minimum important difference is known. But the paper does not recommend 60 participants for 80% power: its ‘Sample size calculations and sensitivity analyses’ example gives 296–518 participants for an 80%-powered main trial. Its smaller pilot-study sample sizes are intended to inform a future trial, not to give the pilot 80% power. (LLM, conf=0.89)
Experimental — accuracy not yet measured
CIs and minimal clinically important differences (MCIDs) are presented to suggest plausible evidence of effect for respective study arms.
“CIs and minimal clinically important differences (MCIDs) are presented to suggest plausible evidence of effect for respective study arms.34 35”
From Mobile Health Biometrics to Enhance Exercise and Physical Activity Adherence in Type 2 Diabetes (MOTIVATE-T2D): a decentralised feasibility randomised controlled trial delivered across the UK and Canada (2025) · cites this paper as [34]
Lee et al. and Bell et al. suggest using confidence intervals and the minimal clinically important difference to interpret feasibility trials.
“Lee et al35 and Bell et al34 suggest using CIs and the MCID to interpret feasibility trials.”
From Mobile Health Biometrics to Enhance Exercise and Physical Activity Adherence in Type 2 Diabetes (MOTIVATE-T2D): a decentralised feasibility randomised controlled trial delivered across the UK and Canada (2025) · cites this paper as [34]
The method of setting the pilot trial sample size was applied.
“The method of setting the pilot trial sample size was applied [49,50], and the following parameters were chosen to establish the sample size:”
From HAPPY MAMA Project (Part 2)—Maternal Distress and Self-Efficacy: A Pilot Randomized Controlled Field Trial (2022) · cites this paper as [49]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Recruitment rate uses potential rather than eligible participants
Minor
The text says 60 participants met eligibility criteria and 50 agreed to participate. That is 83.3% of eligible participants, not the reported 50%; 50% is the proportion of the 100 potential participants.
Reported 50 · recomputed 83.333333

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Developing and evaluating complex interventions: the new Medical Research Council guidance
Craig, P., Dieppe, P., Macintyre, S., Michie, S., Nazareth, I., & Petticrew, M. (2008) · BMJ · doi:10.1136/bmj.a1655 · Cited by 10,995 · see citing works
The functional assessment of cancer therapy scale: development and validation of the general measure
Cella, D. F., Tulsky, D. S., Gray, G., Sarafian, B., Linn, E., Bonomi, A., Silberman, M., Yellen, S. B., Winicour, P., & Brannon, J. (1993) · Journal of Clinical Oncology · doi:10.1200/jco.1993.11.3.570 · Cited by 6,020 · see citing works
CONSORT 2010 statement: extension to randomised pilot and feasibility trials.
Eldridge, S. M., Chan, C. L., Campbell, M. J., Bond, C. M., Hopewell, S., Thabane, L., & Lancaster, G. A. (2016) · BMJ · doi:10.1136/bmj.i5239 · Cited by 3,404 · see citing works
A tutorial on pilot studies: the what, why and how
Thabane, L., Ma, J., Chu, R., Cheng, J., Ismaila, A., Rios, L. P., Robson, R., Thabane, M., Giangregorio, L., & Goldsmith, C. H. (2010) · BMC Medical Research Methodology · doi:10.1186/1471-2288-10-1 · Cited by 3,384 · see citing works
CONSORT 2010 statement: extension to randomised pilot and feasibility trials
on behalf of the PAFS consensus group, Eldridge, S. M., Chan, C. L., Campbell, M. J., Bond, C. M., Hopewell, S., Thabane, L., & Lancaster, G. A. (2016) · Pilot and Feasibility Studies · doi:10.1186/s40814-016-0105-8 · Cited by 2,843 · see citing works
Design and analysis of pilot studies: recommendations for good practice
Lancaster, G. A., Dodd, S., & Williamson, P. R. (2004) · Journal of Evaluation in Clinical Practice · doi:10.1111/j..2002.384.doc.x · Cited by 2,572 · see citing works
Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable
Whitehead, A. L., Julious, S. A., Cooper, C. L., & Campbell, M. J. (2016) · Statistical Methods in Medical Research · doi:10.1177/0962280215588241 · Cited by 1,936 · cited 2× · see citing works
“Whitehead et al 27 showed how, if you know the main trial’s target effect size, you can estimate the pilot study’s optimum sample size, minimizing the number of patients recruited across the two studies.”
Self-citation
The Functional Assessment of Chronic Illness Therapy (FACIT) Measurement System: properties, applications, and interpretation.
(2003) · Health and Quality of Life Outcomes · doi:10.1186/1477-7525-1-79 · Cited by 1,506 · see citing works
What is a pilot or feasibility study? A review of current practice and editorial policy
Arain, M., Campbell, M. J., Cooper, C. L., & Lancaster, G. A. (2010) · BMC Medical Research Methodology · doi:10.1186/1471-2288-10-67 · Cited by 1,483 · see citing works
On the use of a pilot sample for sample size determination
Browne, R. H. (1995) · Statistics in Medicine · doi:10.1002/sim.4780141709 · Cited by 1,007 · see citing works
A tutorial on sensitivity analyses in clinical trials: the what, why, when and how
Thabane, L., Mbuagbaw, L., Zhang, S., Samaan, Z., Marcucci, M., Ye, C., Thabane, M., Giangregorio, L., Dennis, B., Kosa, D., et al. (2013) · BMC Medical Research Methodology · doi:10.1186/1471-2288-13-92 · Cited by 893 · see citing works
. Caution regarding the use of pilot studies to guide power calculations for study proposals.
Kraemer, H. C., Mintz, J., Noda, A., Tinklenberg, J., & Yesavage, J. A. (2006) · Archives of General Psychiatry · doi:10.1001/archpsyc.63.5.484 · Cited by 702 · see citing works
A point of minimal important difference (MID): a critique of terminology and methods
King, M. T. (2011) · Expert Review of Pharmacoeconomics & Outcomes Research · doi:10.1586/erp.11.9 · Cited by 653 · see citing works
Sample sizes for clinical trials with normal data.
Julious, S. A. (2004) · Statistics in Medicine · doi:10.1002/sim.1783 · Cited by 605 · see citing works
Self-citation
Informing efficient randomised controlled trials: exploration of challenges in developing progression criteria for internal pilot studies
Avery, K. N. L., Williamson, P. R., Gamble, C., O'Connell Francischetto, E., Metcalfe, C., Davidson, P., Williams, H., & Blazeby, J. M. (2017) · BMJ Open · doi:10.1136/bmjopen-2016-013537 · Cited by 575 · see citing works
The truly remarkable universality of half a standard deviation: confirmation through another look
Norman, G. R., Sloan, J. A., & Wyrwich, K. W. (2004) · Expert Review of Pharmacoeconomics & Outcomes Research · doi:10.1586/14737167.4.5.581 · Cited by 490 · see citing works
Responsiveness and minimal important differences for patient reported outcomes
Revicki, D. A., Cella, D. F., Hays, R. D., Sloan, J. A., Lenderking, W. R., & Aaronson, N. K. (2006) · Health and Quality of Life Outcomes · doi:10.1186/1477-7525-4-70 · Cited by 475 · see citing works
The role of internal pilot studies in increasing the efficiency of clinical trials
Wittes, J. T., & Brittain, E. (1990) · Statistics in Medicine · doi:10.1002/sim.4780090113 · Cited by 440 · see citing works
Sample size calculations for pilot randomized trials: a confidence interval approach
Cocks, K., & Torgerson, D. J. (2013) · Journal of Clinical Epidemiology · doi:10.1016/j.jclinepi.2012.09.002 · Cited by 431 · see citing works
The statistical interpretation of pilot trials: should significance thresholds be reconsidered?
Lee, E. C., Whitehead, A. L., Jacques, R. M., & Julious, S. A. (2014) · BMC Medical Research Methodology · doi:10.1186/1471-2288-14-41 · Cited by 423 · see citing works
Self-citation
A reinvestigation of recruitment to randomised, controlled, multicenter trials: a review of trials funded by two UK funding agencies
Sully, B. G. O., Julious, S. A., & Nicholl, J. (2013) · Trials · doi:10.1186/1745-6215-14-166 · Cited by 410 · see citing works
Self-citation
Handling missing data in RCTs; a review of the top medical journals
Bell, M. L., Fiero, M., Horton, N. J., & Hsu, C.-H. (2014) · BMC Medical Research Methodology · doi:10.1186/1471-2288-14-118 · Cited by 395 · see citing works
Self-citation
Practical and statistical issues in missing data for longitudinal patient-reported outcomes
Bell, M. L., & Fairclough, D. L. (2013) · Statistical Methods in Medical Research · doi:10.1177/0962280213476378 · Cited by 285 · see citing works
Self-citation
Questions asked and answered in pilot and feasibility randomized controlled trials
Shanyinde, M., Pickering, R. M., & Weatherall, M. (2011) · BMC Medical Research Methodology · doi:10.1186/1471-2288-11-117 · Cited by 229 · see citing works
Underpowering in randomized trials reporting a sample size calculation
Vickers, A. J. (2003) · Journal of Clinical Epidemiology · doi:10.1016/s0895-4356(03)00141-0 · Cited by 102 · see citing works
Designing psycho‐oncology randomised trials and cluster randomised trials: variance components and intra‐cluster correlation of commonly used psychosocial measures
Bell, M. L., & McKenzie, J. E. (2012) · Psycho-Oncology · doi:10.1002/pon.3205 · Cited by 97 · see citing works
Self-citation
Pilot Trials in Clinical Research
Loscalzo, J. (2009) · Circulation · doi:10.1161/circulationaha.109.861625 · Cited by 57 · see citing works
Trials in primary care: statistical issues in the design, conduct and evaluation of complex interventions
Lancaster, G., Campbell, M. J., Eldridge, S. M., Farrin, A. J., Marchant, M., Müller, S., Perera, R., Peters, T., Prevost, A. T., & Rait, G. (2010) · Statistical Methods in Medical Research · doi:10.1177/0962280209359883 · Cited by 54 · see citing works
Methods for Specifying the Target Difference in a Randomised Controlled Trial: The Difference ELicitation in TriAls (DELTA) Systematic Review
Hislop, J., Adewuyi, T. E., Vale, L. D., Harrild, K., Fraser, C. M., Gurung, T., Altman, D. G., Briggs, A. H., Fayers, P. M., Ramsay, C. R., et al. (2014) · PLoS Medicine · doi:10.1371/journal.pmed.1001645 · Cited by 36 · see citing works
A Bayesian hierarchical model for multi-level repeated ordinal data: analysis of oral practice examinations in a large anaesthesiology training programme
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A framework for prospectively defining progression rules for internal pilot studies monitoring recruitment
Hampson, L. V., Williamson, P. R., Wilby, M. J., & Jaki, T. (2017) · Statistical Methods in Medical Research · doi:10.1177/0962280217708906 · Cited by 17 · see citing works
Statistical controversies in cancer research: using standardized effect size graphs to enhance interpretability of cancer-related clinical trials with patient-reported outcomes.
Bell, M., Fiero, M., Dhillon, H., Bray, V., & Vardy, J. (2017) · Annals of Oncology · doi:10.1093/annonc/mdx064 · Cited by 15 · see citing works
Self-citation

Flagged first, then by citations

Sorted by citations

Guidance for conducting feasibility and pilot studies for implementation trials
Pearson, N., Naylor, P.-J., Ashe, M. C., Fernandez, M., Yoong, S. L., & Wolfenden, L. (2020) · Pilot and Feasibility Studies · doi:10.1186/s40814-020-00634-w · Cited by 475 · see citing works
A brief overview of pilot studies and their sample size justification
Kunselman, A. R. (2024) · Fertility and Sterility · doi:10.1016/j.fertnstert.2024.01.040 · Cited by 269 · see citing works
Applying mixed methods to pilot feasibility studies to inform intervention trials
Aschbrenner, K. A., Kruse, G. R., Gallo, J. J., & Clark, V. L. P. (2022) · Pilot and Feasibility Studies · doi:10.1186/s40814-022-01178-x · Cited by 188 · see citing works
“Investigators commonly use quantitative metrics such as recruitment and retention rates to determine whether or not pre-specified feasibility criteria and milestones were met to signal that the research can advance to the next stage of testing [7, 13, 16].”
Method
Inflammatory Response in Robotic-Arm-Assisted Versus Conventional Jig-Based TKA and the Correlation with Early Functional Outcomes
Fontalis, A., Kayani, B., Asokan, A. K., Haddad, I. C., Tahmassebi, J. E., Konan, S., Oussedik, S. I., & Haddad, F. S. (2022) · Journal of Bone and Joint Surgery · doi:10.2106/jbjs.22.00167 · Cited by 85 · see citing works
Power Analysis and Exploratory Research
Haile, Z. T. (2023) · Journal of Human Lactation · doi:10.1177/08903344231195625 · Cited by 91 · see citing works
“However, alternative strategies for calculating sample sizes for pilot studies have recently been proposed (Bell et al., 2018; Julious, 2016).”
Background
Feasibility, Acceptability, and Safety of Faecal Microbiota Transplantation in the Treatment of Major Depressive Disorder: A Pilot Randomized Controlled Trial
Green, J. E., Berk, M., Mohebbi, M., Loughman, A., McGuinness, A. J., Castle, D. J., Chatterton, M. L., Perez, J., Strandwitz, P., Athan, E., et al. (2023) · The Canadian Journal of Psychiatry · doi:10.1177/07067437221150508 · Cited by 87 · see citing works
Important differences and meaningful changes for the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog)
Bell, M. L., Dhillon, H. M., Bray, V., & Vardy, J. L. (2018) · Journal of Patient-Reported Outcomes · doi:10.1186/s41687-018-0071-4 · Cited by 66 · see citing works
Self-citation
Determining sample size for pilot trials: a tutorial
Ying, X., Freedland, K. E., Powell, L. H., Stuart, E. A., Ehrhardt, S., & Mayo‐Wilson, E. (2025) · BMJ · doi:10.1136/bmj-2024-083405 · Cited by 55 · see citing works
A feasibility randomised controlled trial of a brief early intervention for adolescent depression that targets emotional mental images and memory specificity (IMAGINE)
Pile, V., Smith, P. A., Leamy, M. C., Oliver, A., Bennett, E., Blackwell, S. E., Meiser‐Stedman, R., Stringer, D., Dunn, B. D., Holmes, E. A., et al. (2021) · Behaviour Research and Therapy · doi:10.1016/j.brat.2021.103876 · Cited by 40 · see citing works
Effects of non-invasive respiratory supports on inspiratory effort in moderate-severe COVID-19 patients. A randomized physiological study
Schifino, G., Vega, M. L., Pisani, L., Prediletto, I., Catalanotti, V., Comellini, V., Bassi, I., Zompatori, M., Ranieri, V. M., & Nava, S. (2022) · European Journal of Internal Medicine · doi:10.1016/j.ejim.2022.04.012 · Cited by 38 · see citing works
“To reach a statistical power of almost 80%, we assumed to enroll 20 subjects with a minimum of 12 subjects having full data available, [15,16, 17].”
Vibrational Spectroscopy Saliva Profiling as Biometric Tool for Disease Diagnostics: A Systematic Literature Review
Derruau, S., Robinet, J., Untereiner, V., Piot, O., Sockalingum, G. D., & Lorimier, S. (2020) · Molecules · doi:10.3390/molecules25184142 · Cited by 37 · see citing works
“Only publications with both a clinically and/or a histopathologically confirmed disease and a control group, each containing more than 20 participants, were included [40,68].”
Result
Effect of Omega-3 Supplementation in Pregnant Women with Obesity on Newborn Body Composition, Growth and Length of Gestation: A Randomized Controlled Pilot Study
Monthé‐Drèze, C., Sen, S., Mouzon, S. H., & Catalano, P. M. (2021) · Nutrients · doi:10.3390/nu13020578 · Cited by 33 · see citing works
“However, the current pilot study’s sample size was optimal in order to inform a future large RCT with 80% power to detect small-tomoderate effect size in fetal adiposity [68].”
Background
A dyadic advance care planning intervention for people with early-stage dementia and their family caregivers in a community care setting: a feasibility trial
Yeung, C. Y., Ho, K. H. M., & Chan, H. Y. L. (2023) · BMC Geriatrics · doi:10.1186/s12877-023-03815-3 · Cited by 31 · see citing works
Group acceptance and commitment therapy for patients and caregivers in psychosis services: Feasibility of training and a preliminary randomized controlled evaluation
Jolley, S., Johns, L. C., O’Donoghue, E., Oliver, J., Khondoker, M., Byrne, M., Butler, L., De Rosa, C., Leal, D., McGovern, J., et al. (2020) · British Journal of Clinical Psychology · doi:10.1111/bjc.12265 · Cited by 26 · see citing works
Evaluation of a web-based resource to improve menstrual health literacy and self-management in young women
Armour, M., Parry, K. A., Curry, C., Ferfolja, T., Parker, M. A., Farooqi, T., MacMillan, F., Smith, C. A., & Holmes, K. (2022) · Journal of Psychosomatic Research · doi:10.1016/j.jpsychores.2022.111038 · Cited by 27 · see citing works
New guidance to improve sample size calculations for trials: eliciting the target difference
Bell, M. L. (2018) · Trials · doi:10.1186/s13063-018-2894-y · Cited by 26 · see citing works
Self-citation
Nasal High‐flow Oxygen Versus Conventional Oxygen Therapy for Acute Severe Asthma Patients: A Pilot Randomized Controlled Trial
Ruangsomboon, O., Limsuwat, C., Praphruetkit, N., Monsomboon, A., & Chakorn, T. (2020) · Academic Emergency Medicine · doi:10.1111/acem.14187 · Cited by 26 · see citing works
“3), and the future main trial would be powered at 90%.(29) However, due to the coronavirus disease 2019 pandemic, trials involving NHF use outside negative-pressure rooms had to be suspended.”
Background
Exercise-therapy and education for individuals one year after anterior cruciate ligament reconstruction: a pilot randomised controlled trial
Patterson, B., Barton, C. J., Culvenor, A. G., Cooper, R., & Crossley, K. M. (2021) · BMC Musculoskeletal Disorders · doi:10.1186/s12891-020-03919-6 · Cited by 30 · see citing works
Pilot randomized controlled trial of eHealth cognitive-behavioral therapy for insomnia among Spanish-speaking breast cancer survivors
Oswald, L. B., Morales-Cruz, J., Eisel, S. L., Rio, J. D., Hoogland, A. I., Ortiz-Rosado, V., Soto-Lopez, G., Rodriguez-Rivera, E., Savard, J., Castro, E., et al. (2022) · Journal of Behavioral Medicine · doi:10.1007/s10865-022-00313-6 · Cited by 27 · see citing works
“To plan for a future RCT with 90% power to detect a medium effect, a sample of 15 participants per arm was considered acceptable (total recruitment goal N = 30) (Bell et al., 2018).”
Background
Mixed-methods findings from the Ngutulu Kagwero (agents of change) participatory comic pilot study on post-rape clinical care and sexual violence prevention with refugee youth in a humanitarian setting in Uganda
Logie, C. H., Okumu, M., Loutet, M. G., Berry, I., Lukone, S. O., Kisubi, N., Mwima, S., & Kyambadde, P. (2022) · Global Public Health · doi:10.1080/17441692.2022.2092178 · Cited by 23 · see citing works
“To assess feasibility (Bell et al., 2018), we collected information on process (e.g. recruitment rates), resources (e.g. retention, survey completion length), management (e.g. time and capacity required to implement intervention), and scienti ﬁ c outcomes (e.g. survey challenges, estimated…”
Method
Assessment of Acceptability and Initial Effectiveness of a Unified Protocol Prevention Program to Train Emotional Regulation Skills in Female Nursing Professionals during the COVID-19 Pandemic
Ferreres-Galán, V., Navarro-Haro, M. V., Peris-Baquero, Ó., Guillén-Marín, S., de Luna-Hermoso, J., & Osma, J. (2022) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph19095715 · Cited by 21 · see citing works
Pilot Trial of a Sleep-Promoting Intervention for Children With Type 1 Diabetes
Jaser, S. S., Bergner, E. M., Hamburger, E., Bhatia, S. H., Lyttle, M., Bell, G. E., Slaughter, J. C., Malow, B. A., & Simmons, J. H. (2020) · Journal of Pediatric Psychology · doi:10.1093/jpepsy/jsaa105 · Cited by 21 · see citing works
“We aimed for a sample of 20 per intervention arm, as we would expect to target small effect sizes in a larger trial (Bell et al., 2018).”
Method
Combining Stochastic Resonance Vibration With Exergaming for Motor-Cognitive Training in Long-Term Care; A Sham-Control Randomized Controlled Pilot Trial
de Bruin, E. D., Baur, H., Bruelhart, Y., Luijckx, E., Hinrichs, T., & Rogan, S. (2020) · Frontiers in Medicine · doi:10.3389/fmed.2020.507155 · Cited by 19 · see citing works
The Surveillance of Physical Activity, Sedentary Behavior, and Sleep: Protocol for the Development and Feasibility Evaluation of a Novel Measurement System
Crowley, P., Ikeda, E., Islam, S. M. S., Kildedal, R., Jacobsen, S. S., Larsen, J. R., Johansson, P. J., Hettiarachchi, P., Aadahl, M., Mork, P. J., et al. (2022) · JMIR Research Protocols · doi:10.2196/35697 · Cited by 19 · see citing works
“Based on the rules of thumb presented in a recent guidance on using pilot studies to inform the design of intervention trials with continuous outcomes, a sample size of approximately 200-250 participants will be required for our evaluation [20].”
Method
i-Move, a personalised exercise intervention for patients with advanced melanoma receiving immunotherapy: a randomised feasibility trial protocol
Hyatt, A., Gough, K., Murnane, A., Au‐Yeung, G., Dawson, T., Pearson, E. J. M., Dhillon, H. M., Sandhu, S. K., Williams, N., Paton, E., et al. (2020) · BMJ Open · doi:10.1136/bmjopen-2019-036059 · Cited by 19 · see citing works
Effects of a Massage Protocol in Tensiomyographic and Myotonometric Proprieties
Pérez‐Bellmunt, A., Labata‐Lezaun, N., Llurda-Almuzara, L., Rodríguez‐Sanz, J., González-Rueda, V., Bueno-Gracía, E., Çelik, D., & López-de–Celis, C. (2021) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph18083891 · Cited by 19 · see citing works
“A pilot study (n = 10) was carried out in order to set the sample calculation [28].”
Method
Third wave treatments for functional somatic syndromes and health anxiety across the age span: A narrative review
Frostholm, L., & Rask, C. U. (2019) · Clinical Psychology in Europe · doi:10.32872/cpe.v1i1.32217 · Cited by 18 · see citing works
Impact of a multimedia website with patient experiences of multiple sclerosis (PExMS) on immunotherapy decision-making: study protocol for a pilot randomised controlled trial in a mixed-methods design
Barabasch, A., Riemann-Lorenz, K., Kofahl, C., Scheiderbauer, J., Eklund, D., Kleiter, I., Kasper, J., Köpke, S., Lezius, S., Zapf, A., et al. (2021) · Pilot and Feasibility Studies · doi:10.1186/s40814-020-00749-0 · Cited by 18 · see citing works
Self-reported health, neuropsychological tests and biomarkers in fully recovered COVID-19 patients vs patients with post-COVID cognitive symptoms: A pilot study
Lawrence, M. R., Arnetz, J. E., Counts, S., Ahmed, A., & Arnetz, B. B. (2025) · PLoS ONE · doi:10.1371/journal.pone.0315486 · Cited by 17 · see citing works
“While formal power calculations are not required for pilot studies [38], it was important to have a sufficient sample size to examine the feasibility of recruiting participants with and without long COVID, and whether differences could be detected between groups [39].”
Ngutulu Kagwero (agents of change): study design of a participatory comic pilot study on sexual violence prevention and post-rape clinical care with refugee youth in a humanitarian setting in Uganda
Logie, C. H., Okumu, M., Lukone, S. O., Loutet, M. G., McAlpine, A., Latif, M., Berry, I., Kisubi, N., Mwima, S., Kyambadde, P., et al. (2021) · Global Health Action · doi:10.1080/16549716.2021.1940763 · Cited by 19 · see citing works
“The primary outcomes to measure feasibility [51] of the Ngutulu Kagwero intervention were: 1) process, including recruitment rates; 2) resources, including retention rates, adherence, comprehension of surveys, length of time for survey completion, management of eligibility criteria; 3) management, including time and c…”
BackgroundMethod
A preliminary trial examining a ‘real world’ approach for increasing physical activity among breast cancer survivors: findings from project MOVE
Caperchione, C. M., Sabiston, C. M., Stolp, S., Bottorff, J. L., Campbell, K. L., Eves, N. D., Ellard, S. L., Gotay, C. C., Sharp, P., Pullen, T., et al. (2019) · BMC Cancer · doi:10.1186/s12885-019-5470-2 · Cited by 16 · see citing works
Acceptance commitment therapy (ACT) for psychological distress associated with inflammatory bowel disease (IBD): protocol for a feasibility trial of the ACTforIBD programme
Evans, S., Olive, L., Dober, M., Knowles, S., Fuller-Tyszkiewicz, M., O, E., Gibson, P., Raven, L., Gearry, R., McCombie, A., et al. (2022) · BMJ Open · doi:10.1136/bmjopen-2021-060272 · Cited by 15 · see citing works
The influence of the simulation environment on teamwork and cognitive load in novice trauma professionals at the emergency department: Piloting a randomized controlled trial
Lapierre, A., Lavoie, P., Castonguay, V., Lonergan, A.-M., & Arbour, C. (2023) · International Emergency Nursing · doi:10.1016/j.ienj.2022.101261 · Cited by 16 · see citing works
Feasibility and efficacy of a digital resilience training: A pilot study of the strengths-based training RESIST
Behrendt, D., Boß, L., Hannibal, S., Kunzler, A., Wessa, M., & Lehr, D. (2023) · Internet Interventions · doi:10.1016/j.invent.2023.100649 · Cited by 15 · see citing works
Randomized Trial on the Effects of a Mindfulness Intervention on Temperament, Anxiety, and Depression: A Multi-Arm Psychometric Study
Poli, A., Maremmani, A. G. I., Gemignani, A., & Miccoli, M. (2022) · Behavioral Sciences · doi:10.3390/bs12030074 · Cited by 17 · see citing works
“Following recommendations to carry out pilot investigations, a minimum sample size of 12 per group was considered [43] in order to carry out our pilot trial [44,45].”
Method
Digital Therapeutic Self‐Management Intervention in Adolescents With Inflammatory Bowel Disease
Hommel, K. A., Ramsey, R. R., Gray, W. N., & Denson, L. A. (2022) · Journal of Pediatric Gastroenterology and Nutrition · doi:10.1097/mpg.0000000000003623 · Cited by 14 · see citing works
“Although this trial was aimed at determining feasibility and preliminary efficacy, we exceeded the recommended sample size (n = 20) for a pilot trial designed to inform a larger efficacy trial with 80% power to detect a medium effect (18).”
Method
Improving the Quality of Pilot/Feasibility Trials Reporting in Pediatric Psychology
Hilliard, M. E., Modi, A. C., & Palermo, T. M. (2021) · Journal of Pediatric Psychology · doi:10.1093/jpepsy/jsab056 · Cited by 14 · see citing works
In-person peer support for critical care survivors: The ICU REcovery Solutions cO-Led through surVivor Engagement (ICURESOLVE) pilot randomised controlled trial
Haines, K. J., Hibbert, E., Skinner, E. H., Leggett, N. E., Holdsworth, C., Abdelhamid, Y. A., Bates, S., Bicknell, E., Booth, S., Carmody, J., et al. (2024) · Australian Critical Care · doi:10.1016/j.aucc.2024.01.006 · Cited by 13 · see citing works
Feasibility and acceptability of a nurse-led telehealth intervention (BOLSTER) to support patients with peritoneal carcinomatosis and their caregivers: A pilot randomized clinical trial
Pozzar, R. A., Enzinger, A. C., Howard, C., Tavormina, A., Matulonis, U. A., Campos, S., Liu, J. F., Horowitz, N., Konstantinopoulos, P. A., Krasner, C. N., et al. (2024) · Gynecologic Oncology · doi:10.1016/j.ygyno.2024.06.001 · Cited by 13 · see citing works
Risk Factors for Failure of Hard Palate Mucoperiosteal Flap Repair of Acquired Oronasal Communication in Dogs: A Pilot Study
Taney, K. G., Smith, M. M., Cummings, N. P., & Lozano, A. J. (2021) · Frontiers in Veterinary Science · doi:10.3389/fvets.2021.762842 · Cited by 12 · see citing works
“, odds ratios) to inform future studies (18).”
Background
Models and benefits of mobile health application to support patient with tuberculosis: A literature review
Latif, A. I., Sjattar, E. L., & Erika, K. A. (2020) · Enfermería Clínica · doi:10.1016/j.enfcli.2019.07.069 · Cited by 12 · see citing works
Prescribing laughter to ameliorate mental health, sleep, and wellbeing in university students: A protocol for a feasibility study of a randomised controlled trial
Gonot-Schoupinsky, F., Garip, G., Sheffield, D., Omar, O., & Arora, T. (2020) · Contemporary Clinical Trials Communications · doi:10.1016/j.conctc.2020.100676 · Cited by 12 · see citing works
Efficacy, Treatment Characteristics, and Biopsychological Mechanisms of Music-Listening Interventions in Reducing Pain (MINTREP): Study Protocol of a Three-Armed Pilot Randomized Controlled Trial
Feneberg, A. C., Kappert, M. B., Maidhof, R. M., Doering, B. K., Olbrich, D., & Nater, U. M. (2020) · Frontiers in Psychiatry · doi:10.3389/fpsyt.2020.518316 · Cited by 12 · see citing works
“Therefore, following the recommendations mentioned in (122, 123) and (124), we decided to test 30 participants in each group.”
Method
A randomised controlled, feasibility study to establish the acceptability of early outpatient review and early cardiac rehabilitation compared to standard practice after cardiac surgery and viability of a future large-scale trial (FARSTER)
Ngaage, D. L., Mitchell, N., Dean, A., Mitchell, A. S., Hinde, S., Akowuah, E., Doherty, P., Nichols, S., Fairhurst, C. M., Flemming, K., et al. (2023) · Pilot and Feasibility Studies · doi:10.1186/s40814-023-01304-3 · Cited by 11 · see citing works
“The ISWT was summarised descriptively at each timepoint, with the standard deviation being estimated alongside an 80% confidence interval in line with current guidance on estimation of standard deviations from feasibility trials [17, 18].”
Method
Vegetable‐enriched bread: Pilot and feasibility study of measurement of changes in skin carotenoid concentrations by reflection spectroscopy as a biomarker of vegetable intake
Amoah, I., Cairncross, C., & Rush, E. C. (2023) · Food Science & Nutrition · doi:10.1002/fsn3.3327 · Cited by 10 · see citing works
Effects of asymmetric nasal high-flow cannula on carbon dioxide in hypercapnic patients: A randomised crossover physiological pilot study
Pisani, L., Vega, M. L., Ageno, E., Prediletto, I., Dongilli, R., Catalanotti, V., Giancotti, G., & Nava, S. (2024) · Pulmonology · doi:10.1080/25310429.2024.2411813 · Cited by 10 · see citing works
Digital mindfulness-based intervention for people with COPD – a multicentre pilot and feasibility RCT
Tschenett, H., Vafai-Tabrizi, F., Zwick, R. H., Valipour, A., Funk, G., & Nater, U. M. (2025) · Respiratory Research · doi:10.1186/s12931-025-03243-4 · Cited by 10 · see citing works
“…randomized controlled trial (step 3), and to gather preliminary data on the intervention’s effects to inform power calculations and determine which observed trends may be promising for further investigation in a future definitive trial (based on recommendations for pilot studies [22–24]).”
Influential
Feasibility of the Palliative Care Education in Assisted Living Intervention for Dementia Care Providers: A Cluster Randomized Trial
Dobbs, D., Yauk, J., Vogel, C. E., Fanfan, D., Buck, H. G., Haley, W. E., & Meng, H. (2023) · The Gerontologist · doi:10.1093/geront/gnad018 · Cited by 10 · see citing works
Mobile Health Biometrics to Enhance Exercise and Physical Activity Adherence in Type 2 Diabetes (MOTIVATE-T2D): a decentralised feasibility randomised controlled trial delivered across the UK and Canada
Hesketh, K., Low, J., Andrews, R., Blitz, S., Buckley, B., Falkenhain, K., Job, J., Jones, C. A., Jones, H., Jung, M. E., et al. (2025) · BMJ Open · doi:10.1136/bmjopen-2024-092260 · Cited by 9 · see citing works
Medical Student Experiences of Engaging in a Psychological Flexibility Skill Training App for Burnout and Well-being: Pilot Feasibility Study
Ditton, E., Knott, B., Hodyl, N., Horton, G., Walker, F. R., & Nilsson, M. (2023) · JMIR Formative Research · doi:10.2196/43263 · Cited by 9 · see citing works
“The collection of these data can provide information about how psychological skill training apps are experienced in real-world contexts among medical student end users [32,34], unexpected methodological issues and barriers [32], and factors that may affect engagement [34,35].”
BackgroundMethod
Effects of a peer co-facilitated educational programme for parents of children with ADHD: a feasibility randomised controlled trial protocol
Mundal, I. P., Gråwe, R. W., Hafstad, H., Cuevas, C. D. L., & Lara‐Cabrera, M. L. (2020) · BMJ Open · doi:10.1136/bmjopen-2020-039852 · Cited by 11 · see citing works
A randomized, controlled, comparative, proof-of-concept study to evaluate the efficacy and safety of Nisha-Amalaki capsules in prediabetic patients for preventing progression to diabetes
Munshi, R., Karande-Patil, S., Kumbhar, D. A., Deshmukh, A., & Hingorani, L. (2023) · Journal of Ayurveda and Integrative Medicine · doi:10.1016/j.jaim.2023.100806 · Cited by 9 · see citing works
“As this was a Proof-of-Concept Study, with no previous clinical results available with this formulation, a sample size of 60 participants (30 in each group) was considered adequate to address the study objectives [47 e 49].”
Method
Feasibility and Clinical Usefulness of the Unified Protocol in Online Group Format for Bariatric Surgery Candidates: Study Protocol for a Multiple Baseline Experimental Design
Quilez-Orden, A. B., Ferreres-Galán, V., & Osma, J. (2020) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph17176155 · Cited by 9 · see citing works
“To calculate the sample size, we drew on a study that proposed stepwise rules of thumb for pilot studies based on the target effect size and the size of the future trial [40].”
Method
Sample size planning for pilot studiesPreprint
Tseng, C., & Sim, D. (2021) · arXiv (Cornell University) · doi:10.48550/arxiv.2105.05483 · Cited by 9 · see citing works
The Relationship between Toxic Leadership Behavior and Employee Silence: A Quantitative StudyPreprint
Coakley, N. (2021) · SSRN Electronic Journal · doi:10.2139/ssrn.3893817 · Cited by 9 · see citing works
Can lifestyle interventions improve Canadian men’s mental health? Outcomes from the HAT TRICK programme
Sharp, P., Stolp, S., Bottorff, J. L., Oliffe, J. L., Hunt, K., & Caperchione, C. M. (2020) · Health Promotion International · doi:10.1093/heapro/daaa120 · Cited by 8 · see citing works
Brief observable anxiety sensitivity treatment: intervention development and a pilot randomized-controlled acceptability and feasibility trial to evaluate a brief intervention for anxiety sensitivity social concerns
Saulnier, K. G., Koscinski, B., Flynt, S., Accorso, C., & Allan, N. P. (2023) · Cognitive Behaviour Therapy · doi:10.1080/16506073.2023.2288551 · Cited by 9 · see citing works
“Despite limitations of using pilot data to estimate expected effect sizes for definitive trials (Bell et al., 2018), these results suggest an RCT could aim for at least a medium effect size.”
Method
Effect of early weight bearing program with conventional physiotherapy on functional outcomes in surgically treated proximal tibia fracture: a pilot randomized controlled trial
Kadam, A., Wani, S. K., Gadekar, G. N., Katage, G., Garg, K., & Mungikar, S. (2024) · Archives of Orthopaedic and Trauma Surgery · doi:10.1007/s00402-024-05347-w · Cited by 9 · see citing works
Feasibility of a 26-Week Exercise Program to Improve Brain Health in Older Adults at Risk for Type 2 Diabetes: A Pilot Study
Furlano, J. A., & Nagamatsu, L. S. (2020) · Canadian Journal of Diabetes · doi:10.1016/j.jcjd.2020.11.001 · Cited by 8 · see citing works
Randomized Trial on the Effects of a Group EMDR Intervention on Narrative Complexity and Specificity of Autobiographical Memories: A Path Analytic and Supervised Machine-Learning Study
Poli, A., Gemignani, A., & Miccoli, M. (2022) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph19137684 · Cited by 8 · see citing works
“In order to conduct our pilot study [63,64], a minimum sample size of 12 per group was considered [65].”
Background
Feasibility of gabapentin as an intervention for neurorecovery after an acute spinal cord injury: Protocol
Wilson, J. R. M., Doty, S., Petitt, J. C., El-Abtah, M. E., Francis, J. J., Sharpe, M. G., Kelly, M. L., & Anderson, K. D. (2022) · Frontiers in Neurology · doi:10.3389/fneur.2022.1033386 · Cited by 8 · see citing works
“Calculating the eligibility rate and the retention rate from this trial will also be helpful in estimating the duration of a future efficacy trial (22).”
BackgroundMethod
Evaluating the feasibility and exploring the efficacy of an emotion-based approach-avoidance modification training (eAAMT) in the context of perceived stress in an adult sample — protocol of a parallel randomized controlled pilot study
Keinert, M., Eskofier, B. M., Schuller, B. W., Böhme, S., & Berking, M. (2023) · Pilot and Feasibility Studies · doi:10.1186/s40814-023-01386-z · Cited by 8 · see citing works
“Therefore, we will include n = 10 participants per study group (i.e., N = 80 in total) as suggested by Bell and colleagues [68] for pilot studies with expected medium to large effect sizes.”
Feasibility and efficacy of a multicomponent exercise medicine programme in patients with pancreatic cancer undergoing neoadjuvant therapy (the EXPAN trial): study protocol of a dual-centre, two-armed phase I randomised controlled trial
Luo, H., Galvao, D. A., Newton, R. U., Tang, C., Dean, A. P., Jasas, K., Johansson, M., Yusoff, I. F., Spry, N. A., & Taaffe, D. R. (2021) · BMJ Open Gastroenterology · doi:10.1136/bmjgast-2021-000642 · Cited by 8 · see citing works
Introspective Meditation before Seeking Pleasurable Activities as a Stress Reduction Tool among College Students: A Multi-Theory Model-Based Pilot Study
Sharma, M., Kanekar, A. S., Batra, K., Hayes, T., & Lakhan, R. (2022) · Healthcare · doi:10.3390/healthcare10040614 · Cited by 9 · see citing works
“01 for a two-tailed test) were established as a priori, given the generally accepted recommendations from previous studies [36,37].”
Comparison of Manual Toothbrushes with Different Bristle Designs in Terms of Cleaning Efficacy and Plaque Control: A Pilot Study
Rahman, H. (2023) · Indian Journal of Community Medicine · doi:10.4103/ijcm.ijcm_404_22 · Cited by 7 · see citing works
“Study procedures According to Melanie L Bell 2018,[11] a sample size of 30 trial participants with 15 in each group was taken for this pilot study.”
Method
Personalised perioperative dosing of ivabradine in noncardiac surgery: a single-centre, randomised, placebo-controlled, double-blind feasibility pilot trial
White, M. J., Zaccaria, I., Ennahdi-Elidrissi, F., Putzu, A., Dimassi, S., Luise, S., Diaper, J., Mulin, S., Baudat, A., Gil-Wey, B., et al. (2024) · British Journal of Anaesthesia · doi:10.1016/j.bja.2024.05.020 · Cited by 7 · see citing works
Randomized controlled trial of SystemCHANGE™ weight management intervention in neurological conditions
Plow, M. A., Moore, S. M., Chang, J. H., Bachhal, E., & Sparks, K. E. (2019) · Patient Education and Counseling · doi:10.1016/j.pec.2019.08.007 · Cited by 7 · see citing works
If We Build It, Will They Come? Challenges of Adapting and Implementing a Smoking Cessation Program for the LGBTQ Community in Southcentral Texas
Williams, R. D., Housman, J. M., & McDonald, J. D. (2020) · Health Promotion Practice · doi:10.1177/1524839919882385 · Cited by 7 · see citing works
An Integrative Behavioral Couple Therapy (IBCT)-Based Conflict Prevention Program: A Pre-Pilot Study with Non-Clinical Couples
Mairal, J. B., Fernández, E. N., & Polanski, T. (2021) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph18199981 · Cited by 7 · see citing works
ASSOCIATIONS BETWEEN DYSGLYCEMIA, RETINAL NEURODEGENERATION, AND MICROALBUMINURIA IN PREDIABETES AND TYPE 2 DIABETES
Kirthi, V., Zuckerman, B. P., Alam, U., Bunce, C., Hopkins, D., & Jackson, T. L. (2021) · Retina · doi:10.1097/iae.0000000000003337 · Cited by 7 · see citing works
Technology-Assisted Stepped-Care to Promote Adherence in Adolescents with Asthma: A Pilot Study
Ramsey, R. R., Plevinsky, J. M., Guilbert, T. W., Carmody, J. K., & Hommel, K. A. (2022) · Journal of Clinical Psychology in Medical Settings · doi:10.1007/s10880-022-09905-5 · Cited by 8 · see citing works
“A target sample size of 30 was set to exceed the recommended sample size (n = 20) for a pilot trial designed to inform a larger efficacy trial with 80% power to detect a medium effect (Bell et al., 2018).”
Perception of Open Science in the Scientific Community of the Republic of Moldova
Țurcan, N., Cuciureanu, G., Cujba, R., Lupu, V., Cheradi, N., & Cojocaru, I. (2022) · Postmodern Openings · doi:10.18662/po/13.4/519 · Cited by 9 · see citing works
“The questions were adapted through a pilot study to validate the feasibility of the study (2017), to test trial methods and procedures (Bell et al., 2018), to meet the understanding of the later targeted large respondents before the distribution (Mahfooz & Othman, 2021) and to estimate the time required to complete th…”
Method
Increasing digital equity to promote online smoking cessation program engagement among rural adults: a randomized controlled pilot trial
Kelpin, S. S., Brockman, T. A., Decker, P. A., Young, A. M., Boehmer, K. R., Nguyen, A., Kamath, C. C., Sauver, J. S., Sinicrope, P. S., Sharma, P., et al. (2024) · Communications Medicine · doi:10.1038/s43856-024-00624-6 · Cited by 6 · see citing works
“Based on sample size recommendations for pilot studies using continuous outcome variables 38 we determined that with 30 participants randomly assigned to each of the three study arms (total N = 90), this sample size would provide greater than 90% power with two-sided 5% signi ﬁ cance to detect a…”
An Entertainment-Education Video and Written Messages to Alleviate Loneliness in Germany: Pilot Randomized Controlled Study
Liu, S., Wegner, L., Haucke, M. N., Gates, J., Adam, M., & Bärnighausen, T. (2023) · JMIR Formative Research · doi:10.2196/43036 · Cited by 6 · see citing works
“size was at least 50 participants per arm, which would be sufficient to evaluate the study design feasibility [57-60].”
Mindfulness in sex therapy and intimate relationships: a feasibility and randomized controlled pilot study in a cross-diagnostic group
Krieger, J. F., Kristensen, E., Marquardsen, M., Ofer, S., Mortensen, E. L., & Giraldi, A. G. E. (2023) · Sexual Medicine · doi:10.1093/sexmed/qfad033 · Cited by 6 · see citing works
Cancer-related cognitive impairment and wellbeing in patients with newly diagnosed aggressive lymphoma compared to population norms and healthy controls: an exploratory study
Gates, P., Dhillon, H. M., Krishnasamy, M., Wilson, C. J., & Gough, K. (2024) · Supportive Care in Cancer · doi:10.1007/s00520-024-08441-2 · Cited by 6 · see citing works
Efficacy of the Spanish modified Story Memory Technique in Mexicans with multiple sclerosis: A pilot randomized controlled trial
Krch, D., Lequerica, A. H., Arelis, A. A., Barajas, B. V. R., Arango‐Lasprilla, J. C., & Chiaravalloti, N. D. (2019) · Neurorehabilitation · doi:10.3233/nre-192808 · Cited by 6 · see citing works
“We utilized a method recommended by several authors (Bell, Whitehead, & Julious, 2018; Cocks & Torgerson, 2013) that estimates the pilot sample size based upon the target effect size of a future trial.”
A Comparison of the Timing of Hand Expressing of Human Milk With Breast Massage to Standard Care for Mothers of Preterm Infants: An Exploratory Pilot Using a Randomized Controlled Design
Anderson, L. A., Kildea, S. V., Lee, N., Kynoch, K., & Gao, Y. (2022) · Journal of Human Lactation · doi:10.1177/08903344221088789 · Cited by 6 · see citing works
“…general guidelines for pilot studies, including a general rule of at least 30 participants and a minimum sample size of 12 participants per group (Bell et al., 2018; Whitehead et al., 2016); (2) the estimated timeframe to complete the study; and (3) the number of preterm births at the research…”
Background
Including migrant oncology patients in research: A multisite pilot randomised controlled trial testing consultation audio-recordings and question prompt lists
Hyatt, A., Lipson‐Smith, R., Gough, K., Butow, P. N., Jefford, M., Hack, T. F., Hale, S. B., Zucchi, E., White, S. C., Ozoliņš, U., et al. (2022) · Contemporary Clinical Trials Communications · doi:10.1016/j.conctc.2022.100932 · Cited by 6 · see citing works
“Note, however, responses to study measures were not used to estimate the population variance or potential efficacy because the sample size was too small to ensure precise estimation [19].”
Background
Interventions for Increasing Digital Equity and Access (IDEA) among rural patients who smoke: Study protocol for a pragmatic randomized pilot trial
Patten, C. A., Brockman, T. A., Kelpin, S. S., Sinicrope, P. S., Boehmer, K. R., Sauver, J. L. S., Lampman, M. A., Sharma, P., Reinicke, N. M., Huang, M. S., et al. (2022) · Contemporary Clinical Trials · doi:10.1016/j.cct.2022.106838 · Cited by 6 · see citing works
“This sample size will result in > 90% power with two-sided 5% significance to detect a small effect size (~1 standard deviation unit) between study groups for the primary intent-to-treat (ITT) analysis [22].”
Feasibility of a 6-month pilot randomised controlled trial of resistance training on cognition and brain health in Canadian older adults at-risk for diabetes: study protocol
Furlano, J. A., & Nagamatsu, L. S. (2019) · BMJ Open · doi:10.1136/bmjopen-2019-032047 · Cited by 6 · see citing works
Feasibility and acceptability of testing a menstrual-cycle timed smoking cessation intervention for women of reproductive age (Project Phase): Protocol of a pilot randomized controlled trial
Nair, U. S., Miller, E. S., Bell, M. L., ALLEN, S. S., Collins, B. N., & Allen, A. M. (2020) · Contemporary Clinical Trials Communications · doi:10.1016/j.conctc.2020.100569 · Cited by 6 · see citing works
Self-citation
Rationale and study protocol for a randomized controlled trial to determine the effectiveness of a culturally relevant, stress management enhanced behavioral weight loss intervention on weight loss outcomes of black women
Buro, A. W., Baskin, M. L., Miller, D. R., Ward, T., West, D. S., Gore, L. R., Gwede, C. K., Epel, E. S., & Carson, T. L. (2022) · BMC Public Health · doi:10.1186/s12889-022-12519-z · Cited by 6 · see citing works
“As these measures were taken at 3 months, and the current study is assessing 6-month weight loss, larger effects are likely; however, to reduce the likelihood of using an effect size which is too large [29], the study has been powered for a Cohen’s d of 0.”
Background
Testing the feasibility of a guided imagery tobacco cessation intervention delivered by a telephone quitline: Study protocol for a randomized controlled feasibility trial
Gordon, J. S., Giacobbi, P. R., Armin, J. S., Nair, U. S., Bell, M. L., & Alleman, G. P. (2019) · Contemporary Clinical Trials Communications · doi:10.1016/j.conctc.2019.100437 · Cited by 7 · see citing works
“This sample size is large enough to reasonably estimate, in conjunction with sensitivity analysis, relevant variance components, recruitment, and dropout rates for use in a future definitive trial [40,41].”
BackgroundSelf-citation
Using an online intervention to improve menstrual health literacy and self-management in young women: a pilot studyPreprint
Armour, M., Parry, K. A., Curry, C., Ferfolja, T., Parker, M., Farooqi, T., MacMillan, F., Smith, C. T., & Holmes, K. (2021) · Research Square · doi:10.21203/rs.3.rs-841718/v1 · Cited by 6 · see citing works
HAPPY MAMA Project (Part 2)—Maternal Distress and Self-Efficacy: A Pilot Randomized Controlled Field Trial
Mannocci, A., Ciavardini, S., Mattioli, F., Massimi, A., D’Egidio, V., Lia, L., Scaglietta, F., Giannini, A., Antico, R., Dorelli, B., et al. (2022) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph19031461 · Cited by 5 · see citing works
“3 (small effect) [49], namely that the EPDS mean in the IG was lower 4.”
BackgroundMethod
Leveraging Mobile Health to Improve Capecitabine Adherence Among Women With Breast Cancer: A Pilot Randomized Controlled Trial
Graetz, I., Hernandez, S., Arshad, S., Byers, K., Meisel, J. L., Sadigh, G., Sakach, E. A., Gogineni, K., & Torres, M. A. (2024) · JCO Oncology Practice · doi:10.1200/op.24.00031 · Cited by 6 · see citing works
Piloting a team-based telemedicine care for hypertension focused on Black patients
Manandhar, S., Chhetri, S., Sutton, D., Saha, A., Kaur, S., Brown, J., Williamson, J. D., Callahan, K. E., Moore, J. B., Taylor, Y. J., et al. (2025) · Pilot and Feasibility Studies · doi:10.1186/s40814-025-01656-y · Cited by 5 · see citing works
“With an estimated 20% drop out rate [19], 20 patients would allow us to evaluate retention with 18% margin of error at the 95% confidence interval [20, 21].”
Alleviating negative symptoms in schizophrenia using a virtual reality-based therapy targeting social reward learning (ENGAGE): Protocol for a randomised, controlled, assessor-blind pilot study
Donath, V. M., Ries, E. S., Mariegaard, L. S., Kristensen, T. D., Ebdrup, B. H., Strauss, G. P., Fisher, P. M., Rostrup, E., Nordentoft, M., Hilker, R. W., et al. (2025) · PLoS ONE · doi:10.1371/journal.pone.0331632 · Cited by 5 · see citing works
“The sample size of the present feasibility study is set at n = 30 in line with recommendations for pilot studies [41,42].”
Pilot study of an app-supported psychosocial prevention intervention: a mixed-methods approach
Gehrmann, J., Stephan, J., Dehner, J., Stullich, A., Richter, M., PE³PP study group, Ballaschke, O., Finke, F., Gabel, F., Grossmann, A., et al. (2025) · Pilot and Feasibility Studies · doi:10.1186/s40814-025-01737-y · Cited by 5 · see citing works
“This approach is consistent with guidance that pilot studies should be large enough to estimate parameters for a future main study with reasonable precision, but not powered for effectiveness testing [56–60].”
Assessing the feasibility, fidelity and acceptability of a behaviour change intervention to improve tractor safety on farms: protocol for the BeSafe tractor safety feasibility study
Surendran, A., McSharry, J., Meredith, D., McNamara, J. G., Bligh, F., Meade, O., & O’Hora, D. P. (2023) · Pilot and Feasibility Studies · doi:10.1186/s40814-023-01319-w · Cited by 5 · see citing works
Web-based cognitive rehabilitation intervention for cancer-related cognitive impairment following chemotherapy for aggressive lymphoma: protocol for a randomised pilot trial
Gates, P., Green, H. J., Gough, K., Dhillon, H. M., Vardy, J. L., Dickinson, M. J., Guarnera, J., Krishnasamy, M., Livingston, P. M., WHITE, V. M., et al. (2024) · BMJ Open · doi:10.1136/bmjopen-2023-081084 · Cited by 5 · see citing works
“Differences in test/(sub)scale scores at follow-up will be summarised using a mean and 95% CI, as well as 75% and 85% confidence intervals; these will be compared with estimates of minimum clinically important differences, 32 where available.”
BackgroundMethod
Mood and influenza vaccination in older adults: A randomized controlled trial.
Ayling, K., Fairclough, L. C., Buchanan, H., Wetherell, M. A., & Vedhara, K. (2019) · Health Psychology · doi:10.1037/hea0000786 · Cited by 5 · see citing works
“Second, while we note due caution is warranted in overextrapolating effect size estimations from pilot trials (Bell & Julious, 2018; Kraemer, Mintz, Noda, Tinklenberg, & Yesavage, 2015; Leon, Davis, & Kraemer, 2011), effect sizes of the magnitude observed here are not necessarily trivial when the…”
A safety study of intraoperative radiation therapy following stereotactic body radiation therapy and multi-agent chemotherapy in the treatment of localized pancreatic adenocarcinoma: study protocol of a phase I trial
Reddy, A. V., Hill, C., Zheng, L., He, J. P., & Narang, A. K. (2022) · Radiation Oncology · doi:10.1186/s13014-022-02145-9 · Cited by 5 · see citing works
“A sample size of 20 patients was chosen because this will enable safety evaluation using a closely monitored Bayesian stopping rule and is also recommended by the literature [21, 22].”
Method
An Anger-based Approach-Avoidance Modification Training Targeting Dysfunctional Beliefs in Adults with Elevated Stress – Results from a Randomized Controlled Pilot Study
Keinert, M., Schindler‐Gmelch, L., Eskofier, B. M., & Berking, M. (2024) · International Journal of Cognitive Therapy · doi:10.1007/s41811-024-00218-z · Cited by 5 · see citing works
A study protocol for a multicenter randomized pilot trial of a dyadic, tailored, web-based, psychosocial, and physical activity self-management program (TEMPO) for men with prostate cancer and their caregivers
Lambert, S., Duncan, L. R., Ellis, J., Robinson, J. W., Sears, C. S., Culos-Reed, N. S., Matthew, A., de Raad, M., Schaffler, J. L., Mina, D. S., et al. (2021) · Pilot and Feasibility Studies · doi:10.1186/s40814-021-00791-6 · Cited by 5 · see citing works
Diabetes-related outcomes with basal-bolus vs. premixed insulin among veterans with type 2 diabetes: A single institutional retrospective study
Bai, R., Batra, K., Yap, C., & Izuora, K. E. (2023) · The American Journal of the Medical Sciences · doi:10.1016/j.amjms.2023.04.003 · Cited by 5 · see citing works
Women Will Drive the Demand for EVs in the Middle East over the Next 10 Years—Lessons from Today’s Kuwait and 1960s USA
Ottesen, A. R., Banna, S., & Alzougool, B. (2023) · Energies · doi:10.3390/en16093756 · Cited by 5 · see citing works
Feasibility of a Group-Based Telerehabilitation Intervention for Long COVID Management.Preprint
King, M., Byrne, A., Denehy, L., Graham, P. L., Douglas, B., de Toni, P., Santos, A., Kitson, E., Pang, A., Bartos, E. M., et al. (2022) · Research Square · doi:10.21203/rs.3.rs-1452186/v1 · Cited by 5 · see citing works
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Self-citation
Guidelines for designing and evaluating feasibility pilot studies
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Arnold, D. M., Burns, K. E. A., Adhikari, N. K. J., Kho, M. E., Meade, M. O., & Cook, D. J. (2008) · Critical Care Medicine · doi:10.1097/ccm.0b013e3181920e33 · Cited by 214 · see citing works

Authors: Bell, M. L., Whitehead, A. L., & Julious, S. A.
Affiliations: University of Arizona (US)
University of Sheffield (GB)
Corresponding author: Bell, Melanie L
ORCID: Bell, Melanie L
Whitehead, Amy L
Julious, Steven A
Venue: Clinical Epidemiology
Publisher: Informa UK Limited
Published: 2018-01
Volume: Volume 10
Pages: 153-157
ISSN: 1179-1349 (ISSN-L)
DOI: 10.2147/clep.s146397
PMC: PMC5779280
OpenAlex: W2783709266
Semantic Scholar: cfec5aaa40794375792112254874a4c92fb0bf5e
Cited by: 280
References: 32
Citations by year: 2026: 37 · 2025: 52 · 2024: 22 · 2023: 48 · 2022: 43 · 2021: 37 · 2020: 26 · 2019: 12 · 2018: 3
FWCI: 16.18
Type: journal article
Language: en
Open access: gold
doi.org
Licence: cc-by-nc
creativecommons.org/licenses/by-nc/3.0/ (unspecified)
Locations: Clinical Epidemiology (publishedVersion, cc-by-nc)
Europe PMC (PubMed Central) (publishedVersion, cc-by-nc)
PubMed Central (publishedVersion, cc-by-nc)
PubMed (publishedVersion)
White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
ePrints Soton (University of Southampton) (acceptedVersion)
UA Campus Repository (The University of Arizona) (acceptedVersion, cc-by-nc)
Dove Medical Press (Taylor and Francis Group) (submittedVersion, cc-by-nc)
Funders: University of Southampton
National Cancer Institute (P30CA023074)
Topics: Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
Keywords: pilot study, trial design, sample size determination, sensitivity analysis, continuous outcomes, population variance estimation

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Guidance for using pilot studies to inform the design of intervention trials with continuous outcomes

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