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

[Steven Samuels <sjhsamuels@earthlink.net>]

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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