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Re: st: Question on Ttest.


From   Richard Williams <Richard.A.Williams.5@nd.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Question on Ttest.
Date   Fri, 21 Nov 2003 08:09:57 -0500

At 12:47 PM 11/21/2003 +0000, Joao Pedro W. de Azevedo wrote:
Dear Statausers,
I'm doing a simple ttest, however I would like to retrive the Std. Deviation
of the difference of the means (see output below). Does anyone know if Stata
saves this statistic?
Many thanks,
JP


. ttest  match2291_0== match2291_1 if week>=2144
I'm not a heavy-duty Stata user and somebody may be able to give you exactly the answer you want. But, given that this is matched pairs, I think you might be able to improvise as follows:

. gen diff2291 = match2291_0 - match2291_1
. ttest diff2291 == 0 if week>=2144

In other words, compute the difference between the two scores and then do a 1-sample t-test of whether the mean of that difference is zero. From that retrieve the standard error of the difference.


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