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A note on sample size calculations for cluster randomised crossover trials with a fixed number of clusters
Author(s) -
Kelly ThuLan,
Pratt Nicole
Publication year - 2019
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.8191
Subject(s) - sample size determination , crossover , crossover study , cluster (spacecraft) , cluster size , cluster randomised controlled trial , statistics , mathematics , correlation , randomized controlled trial , physics , medicine , computer science , electronic structure , geometry , pathology , quantum mechanics , artificial intelligence , programming language , placebo , alternative medicine
Girardeau, Ravaud and Donner in 2008 presented a formula for sample size calculations for cluster randomised crossover trials, when the intracluster correlation coefficient, interperiod correlation coefficient and mean cluster size are specified in advance. However, in many randomised trials, the number of clusters is constrained in some way, but the mean cluster size is not. We present a version of the Girardeau formula for sample size calculations for cluster randomised crossover trials when the number of clusters is fixed. Formulae are given for the minimum number of clusters, the maximum cluster size and the relationship between the correlation coefficients when there are constraints on both the number of clusters and the cluster size. Our version of the formula may aid the efficient planning and design of cluster randomised crossover trials.