Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: Question about pstest (after running psmatch2)

From   Farasat Bokhari <[email protected]>
To   "[email protected]" <[email protected]>
Subject   st: Question about pstest (after running psmatch2)
Date   Wed, 31 Aug 2011 05:48:18 -0700 (PDT)

I have run the following two codes and have a question
about the second one:
psmatch2 treatmentvar x1 x2 x3 x4, out(outcomevar) logit
pstest x1 x2 x3 x4
The help file for the pstest states that: 
"For each variable in varlist it calculates (a)
t-tests for equality of means in the treated and non-treated groups, both
before and after matching. T-tests are based on a regression of the variable on
a treatment indicator.  Before matching
this is an unweighted regression on the whole sample, after matching the
regression is weighted using the matching weight variable _weight and based on
the on-support sample"
When i try to do this manually, i can replicate the t-value
result for the unmatched case, however, i get a very different t-value for the
matched case.  I did it as follows:
regress x1 treatmentvar
regress x1 treatmentvar if _support == 1 [fw=_weight]
Cant figure out why the t-value on treatmentvar for the
second regression above does not match the output from pstest. 
Any help/insight would be greatly appreciated. 

*   For searches and help try:

© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index