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st: pstest & psmatch2


From   Leela Hebbar <hebbar_stats@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: pstest & psmatch2
Date   Thu, 10 Nov 2005 12:39:26 -0800 (PST)

Can the "pstest" command be used following a
"psmatch2" command that includes the "ate" option?
Specifically, I am using the following:

/**Begin Code**/
psmatch2 itg, out(empl2_4 empl2_8 empl2_12)
pscore(phat) 
noreplacement common ate;

pstest indy_g1 indy_g2 indy_g3 indy_g4 indy_g5 indy_g6
indy_g7 indy_g8 
indy_g9 educ_g1 educ_g2 educ_g3 educ_g4
pre_g1 pre_g2 pre_g3 pre_g4 pre_g5 ten_g1 ten_g2
ten_g3 ten_g4 
atl_reg so_reg no_reg qtr1 qtr2 qtr3 qtr4, sum t(itg)
support(_support);

/**END code**/


I gather the answer is likely no since the
documentation notes "pstest only considered balancing
for the treated" (att). However,if "pstest" can be
used 
following a "psmatch2" with the option "ate", please
read on.  

When I run the above code with the ATE I get very odd
results, and the results  are much more reasonable
when I run the same code without the ATE.  When
invoking the ATE option, I find Pstest yields  control
distributions
that are very different than the treatment
distribution. Moreover only 3 of 219 control
individuals  (i.e. _treatment=0 & support=1) have
weight=1 and the remaining 216  folks have no value
for the weight variable. All of the  219 treatment
individuals have a weight value=1.   

In contrast, when I re-run the psmatch & pstest
command without  the ATE option, the pstest results
make much more sense and all  of the 219 control
individuals 
have a weight value=1.  Also all the 219 treatment
individuals have weight=1. Is there some option I am
missing when running the routine  with ATE?  

Thanks,  

-Leela Hebbar  

******* 
Rutgers University 
Bloustein School of Planning & Public Policy 


		
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