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Re: st: Comparing results from two separate t-tests


From   Richard Goldstein <richgold@ix.netcom.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Comparing results from two separate t-tests
Date   Wed, 12 Mar 2008 15:53:35 -0400

I suggest a regression with an interaction between treatment and group.

Rich

Geoff Wallace wrote:
Dear All,

I have had problems trying to test for whether the treatment effects for two groups of respondents (conservatives and liberals) in a social science experimental questionnaire I am using are significantly different. I used the -ttest- command to obtain the difference of means across the treatment and control group first for the conservative respondent subsample and then repeated the procedure for the liberal respondent subsample. I should also note that I used the –unpaired- option for each command since the data are not paired. The output from the two -ttest- commands yields a separate treatment effect for each subsample. However, I am having trouble figuring out how to use Stata to perform a corresponding ttest on the two separate difference of means. I tried using -est store- after each -ttest- command, but as I expected this option does not appear to work with –ttest-.

Any help would be much appreciated.

Best, Geoff

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