Sample sizes for clinical trials with normal data.
Abstract
This article gives an overview of sample size calculations for parallel group and cross-over studies with Normal data. Sample size derivation is given for trials where the objective is to demonstrate: superiority, equivalence, non-inferiority, bioequivalence and estimation to a given precision, for different types I and II errors. It is demonstrated how the different trial objectives influence the null and alternative hypotheses of the trials and how these hypotheses influence the calculations. Sample size tables for the different types of trials and worked examples are given.
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For a non-inferiority trial with continuous outcomes, a 5% significance level, 80% power, and a non-inferiority margin of Cohen's d = 0.35, the required sample size is 101 participants per group (total N = 202).
“Based on the online calculator (Sealed Envelope Ltd., 2012) developed after the recommendations of Julious (2004), for a 5% significance level, 80% power and a non-inferiority margin of Cohen’s d = 0.35, the sample size required per group is of 101 participants (total N = 202).”
From Can We Boost Treatment Adherence to an Online Transdiagnostic Intervention by Adding Self-Enhancement Strategies? Results From a Randomized Controlled Non-inferiority Trial (2021) · cites this paper as Julious (2004)
For secondary outcomes, the noninferiority margin was set at .5 SD.
“the noninferiority margin for these measures was set at .5 SD,28”
From Telehealth Versus In-Person Acceptance and Commitment Therapy for Chronic Pain: A Randomized Noninferiority Trial. (2017) · cites this paper as Julius, 2004
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- Authors
- Julious, S. A.
- Affiliations
- Northern General Hospital (GB)
- Corresponding author
- Julious, Steven A.
- ORCID
- Julious, Steven A.
- Venue
- Statistics in Medicine
- Publisher
- Wiley
- Published
- 2004-05-21
- Volume
- 23
- Issue
- 12
- Pages
- 1921-1986
- ISSN
- 0277-6715 (ISSN-L)
- 1097-0258
- OpenAlex
- W1997539987
- Cited by
- 605
- References
- 49
- Citations by year
- 2026: 40 · 2025: 51 · 2024: 48 · 2023: 31 · 2022: 36 · 2021: 47 · 2020: 43 · 2019: 46 · 2018: 45 · 2017: 26 · 2016: 32 · 2015: 23 · 2014: 19 · 2013: 20 · 2012: 16
- FWCI
- 1.59
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Statistics in Medicine (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
- Physical Sciences › Mathematics › Statistics and Probability › Probability and Statistical Research
- Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
- Keywords
- sample size determination, clinical trials, normal data, crossover trial, superiority, equivalence, non-inferiority, bioequivalence, type I and type II errors
- MeSH terms
- Biometry, Humans, Research Design, Therapeutic Equivalency, Randomized Controlled Trials as Topic, Sample Size, Cross-Over Studies
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