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Sample size determination for GEE analyses of stepped wedge cluster randomized trials

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  • Fan Li
  • Elizabeth L. Turner
  • John S. Preisser

Abstract

In stepped wedge cluster randomized trials, intact clusters of individuals switch from control to intervention from a randomly assigned period onwards. Such trials are becoming increasingly popular in health services research. When a closed cohort is recruited from each cluster for longitudinal follow‐up, proper sample size calculation should account for three distinct types of intraclass correlations: the within‐period, the inter‐period, and the within‐individual correlations. Setting the latter two correlation parameters to be equal accommodates cross‐sectional designs. We propose sample size procedures for continuous and binary responses within the framework of generalized estimating equations that employ a block exchangeable within‐cluster correlation structure defined from the distinct correlation types. For continuous responses, we show that the intraclass correlations affect power only through two eigenvalues of the correlation matrix. We demonstrate that analytical power agrees well with simulated power for as few as eight clusters, when data are analyzed using bias‐corrected estimating equations for the correlation parameters concurrently with a bias‐corrected sandwich variance estimator.

Suggested Citation

  • Fan Li & Elizabeth L. Turner & John S. Preisser, 2018. "Sample size determination for GEE analyses of stepped wedge cluster randomized trials," Biometrics, The International Biometric Society, vol. 74(4), pages 1450-1458, December.
  • Handle: RePEc:bla:biomet:v:74:y:2018:i:4:p:1450-1458
    DOI: 10.1111/biom.12918
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    Cited by:

    1. Linda J Harrison & Tom Chen & Rui Wang, 2020. "Power calculation for cross‐sectional stepped wedge cluster randomized trials with variable cluster sizes," Biometrics, The International Biometric Society, vol. 76(3), pages 951-962, September.
    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. Dateng Li & Jing Cao & Song Zhang, 2020. "Power analysis for cluster randomized trials with multiple binary co‐primary endpoints," Biometrics, The International Biometric Society, vol. 76(4), pages 1064-1074, December.
    4. Siyun Yang & Mirjam Moerbeek & Monica Taljaard & Fan Li, 2023. "Power analysis for cluster randomized trials with continuous coprimary endpoints," Biometrics, The International Biometric Society, vol. 79(2), pages 1293-1305, June.

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