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Re: st: Stanard Error for Difference in Difference cross-tabulation


From   Steven Samuels <sjhsamuels@earthlink.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Stanard Error for Difference in Difference cross-tabulation
Date   Tue, 10 Feb 2009 12:18:17 -0500

While I agree with Maarten about the analysis procedure, I am unclear about the design- does "one of which" in your description refer to region or to cohort? Was there a treated cohort and a non- treated cohort within each region? Or, were there two cohorts within each region, but with treatment differing between region? Do you have a before/after differences , or are all comparisons cross- sectional?

Please lay out in more detail the design of the study

-Steve


--- On Tue, 10/2/09, Richard Palmer-Jones wrote:
I want to calculate the standard error of the mean
"diffference in difference". I have samples from two
cohorts in each of two regions, one of which received
a treatment, and their respective years of education;
how to I calculate the standard error of the
difference in difference of the years of education?

Looks to me like an interaction effect:
The dummy for cohort tells you how much the average
education differs over cohorts, and you think that
this difference differs across regions, so the
interaction effect between cohort and region gives
you this difference in difference, and -regress- will
automatically give you the standard error.
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