Assuming that you have two dumies called treatment (1=treatment,
0=control) and liberal (1=liberal, 0=conservative), and that your
outcome variable is called y then you want:
anova y treatment liberal treatment*liberal
or:
xi: regress y i.treatment*i.liberal
The two are actually the same.
If you want to read more about this, than the term you are looking for
is "interaction effect".
Hope this helps,
Maarten
--- Geoff Wallace <[email protected]> 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
>
> --
> Geoffrey P.R. Wallace
> Ph.D. Candidate
> Department of Government
> Cornell University
>
> 214 White Hall
> Ithaca, NY 14850
> t.202.302.4209
> f.607.255.4530
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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