<>
Information about -pscore- is easily obtained from
http://www.stata-journal.com/sjpdf.html?articlenum=st0026
Both commands leave variables behind that let you check whether their
propensity scores coincide. Using the famous Lalonde data usually employed
in this kind of exercise -and described in the article above-, I found that
the common support is enforced inconsistenly between the two commands. Then
again, there is no reason to suspect that authors of competing commands
should be consistent among themselves...
*************
use lalonde.dta, clear
qui pscore treat age age2, pscore(mypscore) blockid(myblock) comsup
qui psmatch2 treat age age2, outcome(re78) neighbor(1)
compare _support comsup
---------- difference ----------
count minimum average maximum
------------------------------------------------------------------------
_support=comsup 585
_support>comsup 29 1 1 1
----------
jointly defined 614 0 .0472313 1
----------
total
*************
HTH
Martin
-----Ursprüngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von Sarah Wichmann
Gesendet: Dienstag, 10. März 2009 11:51
An: [email protected]
Betreff: st: psmatch2 and the options ATE and COM
Hello,
I am working with Propensity Score Matching and came across the
following problems (code below).
1) When comparing the results from psmatch2 with pscore (and
subsequently att*), I only get the same results if I do not use the
common support options. If I do that, the results differ. I guess the
common support is selected differently with the two commands, but I
could not find more information. Can somebody explain the difference?
2) When I use psmatch2 again with the common support option, I get
different results for ATT depending on if I also use the ATE option or
not. As I understood the help file, the ATE option should only add
further details in the output instead of changing the calculation,
therefore I do not understand the changing result.
Thanks for your time and consideration,
Sarah
psmatch2 emsbinary logvossd, radius cal(0.1) out(perfbinary) logit com ate
Variable Sample | Treated Controls Difference S.E.
T-stat
----------------------------+-----------------------------------------------
------------
perfbinary Unmatched | .625 .582417582 .042582418
.045186234 0.94
ATT | .612903226 .620169943 -.007266717
.048401842 -0.15
ATU | .581497797 .55933642 -.022161378
ATE | -.018370454
psmatch2 emsbinary logvossd, radius cal(0.1) out(perfbinary) logit com
Variable Sample | Treated Controls Difference S.E.
T-stat
----------------------------+-----------------------------------------------
------------
perfbinary Unmatched | .625 .582417582 .042582418
.045186234 0.94
ATT | .612903226 .620364171 -.007460945
.048395422 -0.15
attr perfbinary emsbinary logvossd, pscore(pscore) logit comsup
n. treat. n. contr. ATT Std. Err. t
---------------------------------------------------------
159 454 0.027 0.046 0.580
--
Sarah Wichmann
Eichelhäherkamp 94b
22397 Hamburg
Handy: 0046 73 683 57 91
0049 173 612 44 42
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