How should a cluster randomized trial be analyzed?

J Epidemiol Popul Health. 2024 Feb;72(1):202196. doi: 10.1016/j.jeph.2024.202196. Epub 2024 Feb 10.


In cluster randomized trials, individuals from the same cluster tend to have more similar outcomes than individuals from different clusters. This correlation must be taken into account in the analysis of every cluster trial to avoid incorrect inferences. In this paper, we describe the principles guiding the analysis of cluster trials including how to correctly account for intra-cluster correlations as well as how to analyze more advanced designs such as stepped-wedge and cluster cross-over trials. We then describe how to handle specific issues such as small sample sizes and missing data.

Keywords: Analysis; Cluster crossover trials; Cluster randomized trials; Stepped-wedge trials.

MeSH terms

  • Cluster Analysis
  • Cross-Over Studies
  • Humans
  • Randomized Controlled Trials as Topic*
  • Research Design*
  • Sample Size