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st: RE: Propensity score balancing property


From   Joe Canner <jcanner1@jhmi.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Propensity score balancing property
Date   Tue, 31 Dec 2013 20:19:09 +0000

Orrin,

I have had this same problem with -pscore-.  My gut feeling is that it is using an overly-conservative definition of "balance", although I'm not sure how to prove such an accusation.  In any case, you may want to try -psmatch2- (also available from SSC) which seems to have a more realistic view of balance.

Regards,
Joe Canner
Johns Hopkins University School of Medicine
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Orrin Pail [orrinpail@gmail.com]
Sent: Tuesday, December 31, 2013 2:46 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: Propensity score balancing property

Hello,

I am trying to use pscore for propensity matching analysis and I am
having difficulties in satisfying the balancing property.

My covariates (xlist below) include 8 different variables. I have been
trying different combinations of them, sometimes removing some, adding
others. I also tried including interaction terms into my xlist but
stata says that they are not allowed. No matter what I do, my
balancing property is not being met.

The closest I get to satisfying the balancing property is when I use
five of the variables. In this case, the output says that the final
number of blocks is 8 and that three of the variables (they are listed
separately) are not balanced in block 7.

Does anyone have any recommendations on how I can satisfy the
balancing property besides adding more variables? From what I
understand, my propensity score analysis would be useless without the
balancing property being met, so I would appreciate all the help!

The command I am using is below (I defined treatment and xlist prior
to this command):

pscore $treatment $xlist, pscore(myscore) blockid(myblock) comsup

Thanks!

Orrin
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