Sample size calculator for cluster randomized trials

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163 Citations (Scopus)


Cluster randomized trials, where individuals are randomized in groups are increasingly being used in healthcare evaluation. The adoption of a clustered design has implications for design, conduct and analysis of studies. In particular, standard sample sizes have to be inflated for cluster designs, as outcomes for individuals within clusters may be correlated; inflation can be achieved either by increasing the cluster size or by increasing the number of clusters in the study. A sample size calculator is presented for calculating appropriate sample sizes for cluster trials, whilst allowing the implications of both methods of inflation to be considered. (C) 2003 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)113-125
Number of pages12
JournalComputers in Biology and Medicine
Issue number2
Publication statusPublished - 2004


  • cluster randomized trial
  • sample size
  • calculator
  • inflation factor
  • CARE


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