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st: cluster() or svy? (analysis of cluster-randomized trials)


From   "Michael I. Lichter" <mlichter@buffalo.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: cluster() or svy? (analysis of cluster-randomized trials)
Date   Mon, 08 Sep 2008 14:18:16 -0400

Hello, friends. I have a question about the analysis of data from cluster-randomized trials (CRTs). CRTs are experiments where subjects are randomly assigned to conditions (control, treatment) based on their group membership rather than being assigned individually as is usually the case in randomized controlled trials. In my study, the clusters are medical practices, so when a medical practice is assigned to a condition, all of the eligible patients therein are also assigned to the condition. CRTs should be analyzed using methods that take account of the clustering in the study design, of course.

My question is this: For CRTs, is there any statistical reason for preferring the cluster() option on estimation commands (e.g., regress, logit) over the survey commands, or vice-versa? I've used both and the results are similar, but the survey commands estimate larger standard errors. If the answer is that they're both equally appropriate but produce different results because they use somewhat different methods of estimation, that's fine.

Thanks.

Michael

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