Re: st: paired t-test on matched sample after propensity score matching

["Michael I. Lichter" <mlichter@buffalo.edu>]

Thomas,

More specifically, you need to merge each matched pair of cases into a 
single record using -reshape wide-. Each pair must have a common id plus 
a flag specifying which is treated and which is untreated. The command 
would look something like -reshape wide outcome, i(id) j(treatflag)-. 
You will probably need to experiment to get just what you want.
Michael

Neil Shephard wrote:
> On Fri, Aug 14, 2009 at 4:59 PM, Weichle, Thomas<Thomas.Weichle@va.gov> wrote:
>   
> > Dear Statalisters,
> > I'm trying to do a paired t-test on a matched sample after performing
> > propensity score matching to assess differences in measured
> > characteristics between treated and untreated individuals.  I've used
> > psmatch2 to perform the matching.  I'm familiar with the syntax to do a
> > paired t-test when there are 2 variables and we want to test whether
> > they differ (ttest varname1 == varname2).  However, the way my data is
> > set up after performing the matching doesn't have 2 separate variables.
> > For example, there is 1 column for each measured characteristic, an
> > indicator for treatment status, and another variable indicating which
> > control the treated was matched to.  Does anyone have any experience
> > trying to perform this matched individuals paired t-test?  Maybe I don't
> > have my data set up correctly.
> >     
> You're correct, you need to -reshape- your data first.  See -man
> reshape- for more information.
>
> Neil
>
>
>   
--
Michael I. Lichter, Ph.D. <mlichter@buffalo.edu>
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 126 / Phone: 716-898-4751 / FAX: 716-898-3536

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