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Comput Biol Med. 2004 Mar;34(2):113-25.

Sample size calculator for cluster randomized trials.

Author information

1
Health Services Research Unit, University of Aberdeen, Polwarth Building Foresterhill, Aberdeen, Scotland AB25 2ZD UK. m.k.campbell@abdn.ac.uk

Abstract

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.

PMID:
14972631
DOI:
10.1016/S0010-4825(03)00039-8
[Indexed for MEDLINE]
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