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Re: st: ttest var1==var2 for clustered data


From   Richard Goldstein <richgold@ix.netcom.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: ttest var1==var2 for clustered data
Date   Tue, 22 Mar 2005 10:04:37 -0500

a regression with the difference as the outcome and no predictors is the same as a paired t-test

Rich

Christian Hunkler wrote:

Dear Rich,

The problem is, we want to perform a mean comparison between two variables
(paired t-test) and not between two subgroups. The syntax without adjusting
for the clustering is  "ttest var1=var2", thus using inflated degrees of
freedom, 'cause no adjustment for the clustering of the data is possible.
In contrast performing the test with a disaggregated file would result in
deflated degrees of freedom...
For our group comparisons we exactly use your proposition.

Best,
Chris


At 22:02 21.03.2005, you wrote:

a t-test is a simple regression where the only predictor is the dummy
variable identifying the groups -- so, put the two variables into one long
variable; add a group identifier and use regression with the cluster option

Rich

Christian Hunkler wrote:

we have network data clustered around egos. Now we want to test for mean
differences in variables that contain proxy information provided by ego
about their alteri. In short a t-test comparison of two variables, but the
observations are not independent but clustered.
I already checked the clttest ado, but it does not yet support comparison
of two variables.
Any ideas, suggestions?
Thanks,
Christian
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