st: Statistical Matching with psmatch2 ?

[Christian Miranda Pacheco <Christian.Miranda@univ-paris1.fr>]

Hi everybody,

I try  to match two different datasets A(contaning variables a)and B  
(containing variables b). using propensity score. They have common  
demographic covariates c(age, sex..) and i would like to use them to  
get a unique dataset, from this form


id    (c)    (a)    (b)
1A     c      a      .
2A     c      a      .
3A     c      a      .
4B     c      .      b
5B     c      .      b
6B     c      .      b

To the merged dataset (a') I try to get _b being the estimated  
variables taken from (b) , T being the tratment status

id    T    (c)    (a)    (b)    (a')
1A    0     c      a      .      a
2A    0     c      a      .      a
3A    0     c      a      .      a
4B    1     c      .      b      _b
5B    1     c      .      b      _b
6B    1     c      .      b      _b

I'am actually using .pscore and .psmatch2
First i get a balanced pscore from,

.pscore T c ,pscore(PSCORE)

Then I include it in the following precedure

.psmatch2 T, outcome(_b) pscore(PSCORE)

The outcome is disapointing, I get _b that are all zero or missing.
I presume it could be that i have a lot of missing values amid the b  
variables, or maybe my specification is just wrong.
Do you have any experience on this?

Thanks!

Christian




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