Cluster Rct Power Calculation. To achieve 90 power with seven clusters in each arm cluster size should be 1383 yielding a total sample size of 19 362 table 1. 6 wherek 0 andk 1 aretherespectivenumbersofcontrolandtreatmentclustersf 0.
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In other situations cluster randomization at the unit or hospital floor level is being considered so the sample size estimates are a little more involved. Jul 14 2017 The exact calculations are shown in Appendix 1. To achieve 80 power with the same number of clusters the required cluster size is only 89 yielding a total sample size of 1246.
Thus the unit of randomization may be different from the unit of analysis.
Jun 30 2011 For a CRCT with a fixed number of clusters k per arm with a fixed number of individuals per cluster m and with power 1 - β then the detectable difference d C follows straightforwardly from equation 1. Nov 01 2012 SE of the treatment effect in a cluster randomized trial as a function of the cluster size n and ICC ρ under the budget constraint B K c sn where B budget K number of clusters c cost per cluster and s cost per person outcome variance σ y 2 100 B 10000 c 300 and s 10. 11 where d I is the detectable difference using individual randomisation and VIF might be either of those presented at equations 5 and 6. The help file is useful and you can install a dialog box for it by following the instructions at the end of the help file.
