Sample size calculation for count outcomes in cluster randomization trials with varying cluster sizes

Jijia Wang, Song Zhang, Chul Ahn

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

In many cluster randomization studies, cluster sizes are not fixed and may be highly variable. For those studies, sample size estimation assuming a constant cluster size may lead to under-powered studies. Sample size formulas have been developed to incorporate the variability in cluster size for clinical trials with continuous and binary outcomes. Count outcomes frequently occur in cluster randomized studies. In this paper, we derive a closed-form sample size formula for count outcomes accounting for the variability in cluster size. We compare the performance of the proposed method with the average cluster size method through simulation. The simulation study shows that the proposed method has a better performance with empirical powers and type I errors closer to the nominal levels.

Original languageEnglish (US)
Pages (from-to)116-124
Number of pages9
JournalCommunications in Statistics - Theory and Methods
Volume49
Issue number1
DOIs
StatePublished - Jan 2 2020

Keywords

  • Sample size
  • cluster randomized trial
  • count outcome

ASJC Scopus subject areas

  • Statistics and Probability

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