Sample size for a two-group comparison of repeated binary measurements using GEE

Sin Ho Jung, Chul W. Ahn

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


Controlled clinical trials often randomize subjects to two treatment groups and repeatedly evaluate them at baseline and intervals across a treatment period of fixed duration. A popular primary objective in these trials is to compare the change rates in the repeated measurements between treatment groups. Repeated measurements usually involve missing data and a serial correlation within each subject. The generalized estimating equation (GEE) method has been widely used to fit the time trend in repeated measurements because of its robustness to random missing and misspecification of the true correlation structure. In this paper, we propose a closed form sample size formula for comparing the change rates of binary repeated measurements using GEE for a two-group comparison. The sample size formula is derived incorporating missing patterns, such as independent missing and monotone missing, and correlation structures, such as AR(1) model. We also propose an algorithm to generate correlated binary data with arbitrary marginal means and a Markov dependency and use it in simulation studies.

Original languageEnglish (US)
Pages (from-to)2583-2596
Number of pages14
JournalStatistics in Medicine
Issue number17
StatePublished - Sep 15 2005


  • AR(1)
  • Independent missing
  • Missing completely at random
  • Monotone missing
  • Working independent correlation

ASJC Scopus subject areas

  • Epidemiology
  • Statistics and Probability


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