Stats
Variable cluster sizes and their impact on sample size calculations (January 3, 2007).
Category: Sample size justification
A recently published article in the International Journal of Epidemiology,
discusses sample size requirements for cluster randomized trials when the size of the
cluster itself varies. The authors develop an approximation that uses the coefficient of
variation (CV) of the distribution of cluster sizes. The authors point out that in many
clinical trials, the CV of the cluster size can be large and that 0.65 is a reasonable
expection. They also point out that when the CV of cluster size is small (less than 0.23) the
effect on sample size calculations is negligible.
07/08/2008.
