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Randomized Controlled Trials 5: Determining the Sample Size and Power for Clinical Trials and Cohort Studies

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Clinical Epidemiology

Part of the book series: Methods in Molecular Biology ((MIMB,volume 1281))

Abstract

Performing well-powered randomized controlled trials is of fundamental importance in clinical research. The goal of sample size calculations is to assure that statistical power is acceptable while maintaining a small probability of a type I error. This chapter overviews the fundamentals of sample size calculation for standard types of outcomes for two-group studies. It considers (1) the problems of determining the size of the treatment effect that the studies will be designed to detect, (2) the modifications to sample size calculations to account for loss to follow-up and nonadherence, (3) the options when initial calculations indicate that the feasible sample size is insufficient to provide adequate power, and (4) the implication of using multiple primary endpoints. Sample size estimates for longitudinal cohort studies must take account of confounding by baseline factors.

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Author information

Authors and Affiliations

  1. Division of Epidemiology, Internal Medicine, School of Medicine, University of Utah, Williams Building, 295 Chipeta Way, Salt Lake City, UT, 84108, USA

    Tom Greene

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  1. Tom Greene
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Correspondence to Tom Greene .

Editor information

Editors and Affiliations

  1. Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada

    Patrick S. Parfrey

  2. Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada

    Brendan J. Barrett

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Greene, T. (2015). Randomized Controlled Trials 5: Determining the Sample Size and Power for Clinical Trials and Cohort Studies. In: Parfrey, P., Barrett, B. (eds) Clinical Epidemiology. Methods in Molecular Biology, vol 1281. Humana Press, New York, NY. https://doi.org/10.1007/978-1-4939-2428-8_13

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  • DOI: https://doi.org/10.1007/978-1-4939-2428-8_13

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  • Publisher Name: Humana Press, New York, NY

  • Print ISBN: 978-1-4939-2427-1

  • Online ISBN: 978-1-4939-2428-8

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