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Power Calculation For Cross-Sectional Stepped Wedge Cluster-Randomized Trials With Variable Cluster Sizes, Linda J. Harrison, Tom Chen, Rui Wang
Power Calculation For Cross-Sectional Stepped Wedge Cluster-Randomized Trials With Variable Cluster Sizes, Linda J. Harrison, Tom Chen, Rui Wang
Harvard University Biostatistics Working Paper Series
Standard sample size calculation formulas for Stepped Wedge Cluster Randomized Trials (SW-CRTs) assume that cluster sizes are equal. When cluster sizes vary substantially, ignoring this variation may lead to an under-powered study. We investigate the relative efficiency of a SW-CRT with varying cluster sizes to equal cluster sizes, and derive variance estimators for the intervention effect that account for this variation under the assumption of a mixed effects model; a commonly-used approach for analyzing data from cluster randomized trials. When cluster sizes vary, the power of a SW-CRT depends on the order in which clusters receive the intervention, which is …