Sample Size Estimation in Clinical Research

Wang, Xiaofeng; Ji, Xinge

doi:10.1016/j.chest.2020.03.010

Cited by 452Statistical Methods in Clinical TrialsStatistical Methods in EpidemiologyMeta-analysis and systematic reviews

Sample Size Estimation in Clinical Research

Wang, Xiaofeng, Ji, Xinge·2020·Chest

DOI 10.1016/j.chest.2020.03.010

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Abstract

Sample size determination is an essential step in planning a clinical study. It is critical to understand that different study designs need different methods of sample size estimation. Although there is a vast literature discussing sample size estimation, incorrect or improper formulas continue to be applied. This article reviews basic statistical concepts in sample size estimation, discusses statistical considerations in the choice of a sample size for randomized controlled trials and observational studies, and provides strategies for reducing sample size when planning a study. To assist clinical researchers in performing sample size calculations, we have developed an online calculator for common clinical study designs. The calculator is available at http://riskcalc.org:3838/samplesize/. Finally, we offer our recommendations on reporting sample size determination in clinical studies.

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The limited power of the effectiveness trials limits interpretation of the mixed findings reported across all trial outcomes.
“This limits interpretation of the mixed findings reported across all of the trial outcomes (Wang & Ji, 2020).”
From A Systematic Review of Third-Wave Therapies to Reduce Distress and Improve Wellbeing and Quality of Life in People with Parkinson's Disease. (2025) · cites this paper as Wang & Ji, 2020

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Yuan, Y., Zhu, Y., Lin, C.-J., Wang, S., Xie, Y.-H., Li, H.-X., Xing, J., Zhao, B., Zhang, M.-M., & You, Z.-Q. (2023) · Science of the Total Environment · doi:10.1016/j.scitotenv.2023.162256 · Cited by 10
“The sample size of investigated restaurants could make the anticipation error 5 % under the premise of 95 % con ﬁ dence interval, which metthe statistical requirements (Wang and Ji, 2020).”
Fluorescence Cholangiography Using Indocyanine Green Improves the Identification of Biliary Structures During Laparoscopic Cholecystectomy
D'Acapito, F., Cucchetti, A., Solaini, L., Serenari, M., Framarini, M., & Ercolani, G. (2022) · World Journal of Surgery · doi:10.1007/s00268-022-06854-w · Cited by 10 · see citing works
Distinguishing swept-source optical coherence tomography findings in active toxoplasmic retinochoroiditis
Ksiaa, I., Khochtali, S., Mefteh, M., Fredj, M. B., Amor, H. B., Abroug, N., & Khairallah, M. (2021) · Eye · doi:10.1038/s41433-021-01491-4 · Cited by 10 · see citing works
Systemic Inflammation and Oxidative Stress in Childhood Obesity: Sex Differences in Adiposity Indices and Cardiovascular Risk
Petek, T. H., Homšak, E., Svetej, M., & Varda, N. M. (2024) · Biomedicines · doi:10.3390/biomedicines13010058 · Cited by 9 · see citing works
“The sample size was determined using an online calculator available on the Cleveland Clinic website, based on a published article [26], with an alpha value of 0.05 and a power of 80%.”
Influential
A best practices framework for spatial biology studies in drug discovery and development: enabling successful cohort studies using digital spatial profiling
Krull, D., Haynes, P., Kesarwani, A. K., Tessier, J., Chen, B. J., Hunter, K., Rodriguez, D., Liang, Y., Mansfield, J. R., McClain, M., et al. (2024) · Journal of Histotechnology · doi:10.1080/01478885.2024.2391683 · Cited by 9
“This process is dependent on the type and sub-types of the study designs, the type of outcome, and a specified hypothesis test [27].”
Effects of Intermittent Hypoxia Protocols on Cognitive Performance and Brain Health in Older Adults Across Cognitive States: A Systematic Literature Review
Boulares, A., Pichon, A., Faucher, C., Bragazzi, N., & Dupuy, O. (2024) · Journal of Alzheimer's Disease · doi:10.3233/jad-240711 · Cited by 9 · see citing works
Impact of mobile health technologies on human papillomavirus vaccination uptake among mothers of unvaccinated girls aged 9–14 years in Lagos, Nigeria (mHealth-HPVac): study protocol of a randomised controlled trial
Okunade, K., Adejimi, A., Adekanye, T., Allsop, M. J., Adelabu, H., Thomas-Ogodo, O., Onyeka, T., Lawanson, T., Akaba, G. O., Salako, O., et al. (2024) · BMC Cancer · doi:10.1186/s12885-024-12538-6 · Cited by 9
“…of 28.5% for a usual care condition derived from the systematic review by Asgedom et al [19] and an expected attrition rate of 20%, a sample size [20] of n = 123 women is expected to provide 80% power to establish a 30% proportional difference in HPV vaccination uptake between mHealth…”
MethodInfluential
Comparison of artificial intelligence algorithm for the diagnosis of hip fracture on plain radiography with decision-making physicians: a validation study
Beyaz, S., Yayli, S. B., Kılıç, E., & Kılıç, K. (2024) · Acta Orthopaedica et Traumatologica Turcica · doi:10.5152/j.aott.2024.23065 · Cited by 9
Sample size considerations in research
Sivasamy, S. (2023) · Endodontology · doi:10.4103/endo.endo_235_23 · Cited by 9
Investigation of the association between habitual dietary FODMAP intake, metabolic parameters, glycemic status, and anthropometric features among apparently healthy overweight and obese individuals
Hemami, R. M., Shakarami, A., Ardekani, A. M., Aghaii, S., Makarem, D., Nikrad, N., Farhangi, M. A., & Abbasi, M. S. P. (2023) · BMC Endocrine Disorders · doi:10.1186/s12902-023-01458-4 · Cited by 7 · see citing works
Perioperative nutritional risk and its influencing factors in patients with oral cancer: a longitudinal study
Wang, G.-F., Ou, M., Chen, H., Zhu, S.-J., Chen, Y.-Y., & Xu, X.-H. (2023) · Frontiers in Nutrition · doi:10.3389/fnut.2023.1200820 · Cited by 9
The Impact of Mobility on Shopping Preferences during the COVID-19 Pandemic: The Evidence from the Slovak Republic
Harantová, V., Kalašová, A., Kubíková, S., Mazanec, J., & Jordová, R. (2022) · Mathematics · doi:10.3390/math10091394 · Cited by 9 · see citing works
Initial Insights into the NET-Associated ceRNA Network in Pulpitis: Transcriptomic and Functional Exploration
Guo, X.-L., Wu, K.-L., Dang, L.-R., Liu, S.-T., Xu, J., Wang, R., Xu, J.-Y., Zhong, Y.-M., Chen, Z., & Wu, B.-L. (2025) · International Dental Journal · doi:10.1016/j.identj.2025.100958 · Cited by 8
“40 Without longitudinal sampling or reﬁned clinical staging, it remains difﬁcult to determine whether the observed regulatory changes are stage-spe-ciﬁc or reﬂect broader disease-associated trends.”
Chronic postsurgical pain in young children: Prevalence, pain trajectories and physical and psychological prognostic factors
Ceniza-Bordallo, G., Fraile, A. G., López-de-Uralde-Villanueva, I., Rabbitts, J., Li, R., Palermo, T. M., & Martín-Casas, P. (2025) · Journal of Pain · doi:10.1016/j.jpain.2025.105476 · Cited by 8 · see citing works
The prevalence of myopia and eye health behaviors among 3 to 18 years: a cross-sectional survey study
Tian, L., Zhu, M., Song, Y., Wang, Y., & Jiang, Y. (2025) · BMC Public Health · doi:10.1186/s12889-025-22906-x · Cited by 8
Endotyping Insulin–Glucose Homeostasis in Hidradenitis Suppurativa: The Impact of Diabetes Mellitus and Inflammation
Rached, N. A., Dietrich, J. W., Ocker, L., Stockfleth, E., Haven, Y., Myszkowski, D., & Bechara, F. (2025) · Journal of Clinical Medicine · doi:10.3390/jcm14072145 · Cited by 8 · see citing works
“The calculation of the sample size was based on Wang et al. [33], which is available at https://riskcalc.org/samplesize/ (accessed on 1 June 2023).”
Factors related to sedentary behavior in older adult stroke patients in China: a study based on decision tree and logistic regression model
Liu, S., Li, J., Chen, X., Jiang, X., Tang, R., & Lv, Y. (2024) · Frontiers in Public Health · doi:10.3389/fpubh.2024.1457151 · Cited by 8 · see citing works
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Geng, X., Dong, Z., Li, Y., Zhao, M.-W., Liu, Y.-Q., Li, Z.-J., Cai, H., Zhang, M., Yan, X.-F., Sun, Z., et al. (2024) · Orthopaedic Surgery · doi:10.1111/os.14277 · Cited by 8
Targeted psychological and psychosocial interventions for auditory hallucinations in persons with psychotic disorders: Protocol for a systematic review and meta-analysis
Fässler, L., Bighelli, I., Leucht, S., Sabé, M., Bajbouj, M., Knaevelsrud, C., & Böge, K. (2024) · PLoS ONE · doi:10.1371/journal.pone.0306324 · Cited by 11 · see citing works
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Ababneh, O., Bsisu, I. K., El-Share', A. I., Alrabayah, M., Qudaisat, I., Alghanem, S. M., Khreesha, L. A., Ali, A., & Rashdan, M. Z. (2023) · Healthcare · doi:10.3390/healthcare11212818 · Cited by 8
“The required sample size was calculated using Sample Size Calculator (http://riskcalc.org: 3838/samplesize/#, accessed on 1 March 2021) [40].”
Method
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Sermsaksasithorn, P., Asawanonda, P., Phutrakool, P., Ondee, T., Chariyavilaskul, P., Payungporn, S., Pongpirul, K., & Hirankarn, N. (2023) · medRxiv · doi:10.1159/000539492 · Cited by 8 · see citing works
“Categorical data will be expressed as a number and depending on which is more appropriate, continuous data will be reported as mean +/ − standard deviation or median +/ − interquartile range.”
Background
Analysis of Postural Stability Following the Application of Myofascial Release Techniques for Low Back Pain—A Randomized-Controlled Trial
Ożóg, P., Weber-Rajek, M., Radzimińska, A., & Goch, A. (2023) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph20032198 · Cited by 8 · see citing works
“The sample size was calculated by the formula for the minimum sample size (Nmin) [32]:”
Method
A Randomized Clinical Trial to Assess the Efficacy of a Psychological Treatment to Quit Smoking Assisted with an App: Study Protocol
López‐Durán, A., Becoña, E., Senra, C., Suárez-Castro, D., Barroso-Hurtado, M., & Martínez-Vispo, C. (2022) · International Journal of Environmental Research and Public Health · doi:10.3390/ijerph19159770 · Cited by 9 · see citing works
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Yi, A., Qin, X., Du, Z.-Y., Wang, T.-S., & Liu, F. (2021) · Evidence-Based Complementary and Alternative Medicine · doi:10.1155/2021/3926822 · Cited by 8
“According to previous reports [9, 10], each group requires at least 30 cases.”
Method
Retracted
Effect of Topical Capsaicin on Painful Sensory Peripheral Neuropathy in Patients with Type 2 Diabetes: A Double-Blind Placebo-Controlled Randomised Clinical Trial
Agoons, B., Yefou, M. D., Katte, J., Etoga, M. E., Agoons, D., Yepnjio, F., Boli, A., Wasnyo, Y., Sobngwi, E., & Mbanya, J. (2020) · Cureus · doi:10.7759/cureus.11147 · Cited by 8 · see citing works
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Fabbri, A., Ruggeri, E., Virtuoso, A., Giannarelli, D., Raso, A., Chegai, F., Remotti, D., Signorelli, C., & Nelli, F. (2025) · Cancers · doi:10.3390/cancers17121948 · Cited by 7
“The sample size calculator tailored for observational cohort studies was utilized to determine the number of patients needed for this analysis [31].”
Optimal timing of cancer treatments: a call for emerging evidence from clinical trials and real-world studies
Zhang, J.-R., Venchiarutti, R., Wang, X.-F., & He, Q.-H. (2025) · British Journal of Cancer · doi:10.1038/s41416-025-03030-4 · Cited by 7 · see citing works
Self-citation
Exploring the role of inflammatory biomarkers in trigeminal neuralgia
Lai, S.-L., Li, H., Xing, Y., Wu, D., Wang, L., & Liang, Q. (2024) · Brain, Behavior, & Immunity - Health · doi:10.1016/j.bbih.2024.100930 · Cited by 7
Long-term distress throughout one’s life: health-related quality of life, economic and caregiver burden of patients with neurofibromatosis type 1 in China
Liang, W.-X., Cao, S.-H., Suo, Y.-S., Zhang, L.-N., Yang, L., Wang, P., Wang, H.-F., Wang, H.-F., Bai, G.-N., Li, Q., et al. (2024) · Frontiers in Public Health · doi:10.3389/fpubh.2024.1398803 · Cited by 7 · see citing works
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Park, B., Choi, Y., Lee, J., Ahn, Y., Lee, E. J., & Son, C. (2024) · General Hospital Psychiatry · doi:10.1016/j.genhosppsych.2024.08.001 · Cited by 8 · see citing works
The effects of electroencephalography functional connectivity during emotional recognition among patients with major depressive disorder and healthy controls
Yuan, E. J., Chang, C. H., Chen, H.-H., & Huang, S. (2024) · Journal of Psychiatric Research · doi:10.1016/j.jpsychires.2024.02.003 · Cited by 8 · see citing works
Suboptimal reliability of FIB‐4 and NAFLD‐fibrosis scores for staging of liver fibrosis in general population
Hazzan, R., Ahmad, N. A., Habib, A. S., Saleh, I., & Ziv, N. (2024) · JGH Open · doi:10.1002/jgh3.13034 · Cited by 7 · see citing works
Evaluation of molecular receptors status in breast cancer using an mpMRI-based feature fusion radiomics model: mimicking radiologists’ diagnosis
Lai, S., Liang, F., Zhang, W.-L., Zhao, Y., Li, J.-M., Zhao, Y.-D., Xu, Y., Ding, W., Zhan, J., Zhen, X., et al. (2023) · Frontiers in Oncology · doi:10.3389/fonc.2023.1219071 · Cited by 7
D-DI/PLT can be a prognostic indicator for sepsis
Zhao, X., Wu, X., Si, Y., Xie, J.-G., Wang, L.-X., Liu, S.-S., Duan, C., Wang, Q.-M., Wu, D., Wang, Y., et al. (2023) · PeerJ · doi:10.7717/peerj.15910 · Cited by 7 · see citing works
Balanced crystalloids (RInger’s lactate) versus normal Saline in adults with diabetic Ketoacidosis in the Emergency Department (BRISK-ED): a protocol for a pilot randomized controlled trial
Yan, J. W., Slim, A., Aarsen, K. V., Choi, Y.-H., Byrne, C., Poonai, N., Collins, H., & Clemens, K. (2023) · Pilot and Feasibility Studies · doi:10.1186/s40814-023-01356-5 · Cited by 7
Very High Yield of Urgent Small-Bowel Capsule Endoscopy for Ongoing Overt Suspected Small-Bowel Bleeding Irrespective of the Usual Predictive Factors
Estevinho, M., Pinho, R., Rodrigues, A., Ponte, A., Afecto, E., Correia, J., & Freitas, T. (2022) · Diagnostics · doi:10.3390/diagnostics12112685 · Cited by 7 · see citing works

Authors: Wang, X., & Ji, X.
Affiliations: Cleveland Clinic (US)
Corresponding author: Wang, Xiaofeng
ORCID: Wang, Xiaofeng
Venue: Chest
Publisher: Elsevier BV
Published: 2020-07
Volume: 158
Issue: 1
Pages: S12-S20
ISSN: 0012-3692 (ISSN-L)
DOI: 10.1016/j.chest.2020.03.010
OpenAlex: W3039422431
Cited by: 452
References: 0
Citations by year: 2026: 87 · 2025: 105 · 2024: 121 · 2023: 76 · 2022: 36 · 2021: 22 · 2020: 4 · 2012: 1
FWCI: 24.19
Type: journal article
Language: en
Open access: closed
Licence: www.elsevier.com/tdm/userlicense/1.0/ (tdm)
www.elsevier.com/legal/tdmrep-license (tdm)
Locations: CHEST Journal (publishedVersion)
PubMed (publishedVersion)
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: sample size determination, randomized controlled trials, observational studies, clinical research design, statistical power
MeSH terms: Humans, Research Design, Randomized Controlled Trials as Topic, Sample Size, Observational Studies as Topic

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Sample Size Estimation in Clinical Research

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