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Abstract

We describe five asymptotically unbiased estimators of intervention effects on event rates in nonmatched and matched-pair cluster randomized trials, and we present a bias-corrected version of the estimators for use when the number of clusters is small. The estimators are the ratio of mean counts (r ₁), ratio of mean cluster-level event rates (r ₂), ratio of event rates (r ₃), double ratio of counts (r ₄), and double ratio of event rates (r ₅). r ₁, r ₂, and r ₃ estimate the total effect, which comprises the direct and indirect effects; r ₄ and r ₅ estimate the direct effect. We describe a new command, crtrest, that provides these ratio estimators and their standard errors in nonmatched and matched-pair cluster randomized trials.

Keywords

st0695 crtrest ratio estimator intervention effects event rate cluster randomized trial

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crtrest: A command for ratio estimators of intervention effects on event rates in cluster randomized trials

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