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Sample size and power calculations using the noncentral t-distribution

Author

Listed:
  • David A. Harrison

    (ICNARC, London)

  • Anthony R. Brady

    (ICNARC, London)

Abstract

The standard formulas for sample size and power calculation, as implemented in the command sampsi, make use of a normal approximation to the t-distribution. When the sample sizes are small, this approximation is poor, resulting in overestimating power (or underestimating sample size). One particular situation in which this is likely to be important is the field of cluster randomized trials. Although the total number of individuals in a cluster randomized trial may be large, the number of clusters will often be small. We present a simulation study from the design of a cluster randomized crossover trial that motivated this work and a command to perform more accurate sample size and power calculations based on the noncentral t-distribution. Copyright 2004 by StataCorp LP.

Suggested Citation

  • David A. Harrison & Anthony R. Brady, 2004. "Sample size and power calculations using the noncentral t-distribution," Stata Journal, StataCorp LP, vol. 4(2), pages 142-153, June.
    • Handle: RePEc:tsj:stataj:v:4:y:2004:i:2:p:142-153
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    Cited by:

    1. Nadini Persaud & Indeira Persaud, 2016. "The Relationship between Socio-Demographics and Stress Levels, Stressors, and Coping Mechanisms among Undergraduate Students at a University in Barbados," International Journal of Higher Education, Sciedu Press, vol. 5(1), pages 1-11, February.
    2. Kendra Davis‐Plourde & Monica Taljaard & Fan Li, 2023. "Sample size considerations for stepped wedge designs with subclusters," Biometrics, The International Biometric Society, vol. 79(1), pages 98-112, March.
    3. Denes Szucs & John P A Ioannidis, 2017. "Empirical assessment of published effect sizes and power in the recent cognitive neuroscience and psychology literature," PLOS Biology, Public Library of Science, vol. 15(3), pages 1-18, March.
    4. Víctor Gómez-Valenzuela, 2022. "Intellectual capital factors at work in Dominican firms: understanding their influence," Journal of Innovation and Entrepreneurship, Springer, vol. 11(1), pages 1-24, December.

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