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

From   "Austin Nichols" <>
Subject   Re: st: cluster() or svy? (analysis of cluster-randomized trials)
Date   Mon, 8 Sep 2008 14:30:03 -0400

Michael I. Lichter <>:
If the clustering is all you're fixing, then -svy- and the -cluster-
option should give you the same answer.  Is there more to your story?

webuse nhanes2
egen c=group(strata psu)
svyset c
svy: reg bpsystol height weight
reg bpsystol height weight, cl(c)

On Mon, Sep 8, 2008 at 2:18 PM, Michael I. Lichter <> wrote:
> 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.
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