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Sample size calculations for cluster randomised controlled trials with a fixed number of clusters

Karla Hemming*, Alan J Girling, Alice J Sitch, Jennifer Marsh and Richard J Lilford

BMC Medical Research Methodology 2011, 11:102  doi:10.1186/1471-2288-11-102

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Further early references to sample sizes with fixed number of clusters

Michael Campbell   (2011-09-12 16:34)  University of Sheffield email

Hemming et al (2011) give a useful review of sample size calculations with a fixed number of clusters. As they acknowledge their equations (17) to (19) are derived from Donner and Klar (200). I would like to point out the issue of fixed number of clusters was also discussed by Campbell (2000) that the authors’ equation (13) was first given as equation (2) in that paper and as equation (9.7) in Machin and Campbell (2005).

Mike Campbell

References
Campbell MJ Cluster randomized trials in general (family) practice research. Statistical Methods in Medical Research 2000, 9; 81-94

Donner A and Klar N. Design and analysis of cluster randomized trials. London, Arnold 2000

Machin D and Campbell MJ Design of Studies for Medical Research. Chichester, John Wiley and Sons Ltd, 2005

Competing interests

None

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