st: psmatch2 with exact matching

[Charles Stoecker <cfstoecker@ucdavis.edu>]

Hi Statalist,

I'm using the add-on psmatch2 (by Barbara Sinansei and Edwin Leuven -
ssc install psmatch2) to conduct propensity score matching.  I would
like to use it to conduct an exact match on state and then further
match by propensity scores within state.  In the helpfile for the
command it indicates this can be done with:
        g att = .
        egen g = group(groupvars)
        levels g, local(gr)
        qui foreach j of local gr {
                psmatch2 treatvar varlist if g==`j', out(outvar)
                replace att = r(att) if  g==`j'
        }
        sum att

This will provide the estimate of the difference between treatment and
control groups.  My question is, how do I get the standard error of
the estimated difference?

Thanks!
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