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Re: st: RES: examples propensity score matching


From   Ana Gabriela Guerrero Serdan <ag_guerreroserdan@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RES: examples propensity score matching
Date   Wed, 29 Oct 2008 15:40:32 -0700 (PDT)

Thanks Henrique, 

I want to match individuals (treatment and control groups) in t2 (post treatment) with individuals  in t1 (pre-treatment) sing several covariates (observable characteristics).  So in this case I would be able to apply double difference.  

So how can I be assured that the matched individuals are different for the treatment and control groups? 



--- On Tue, 10/28/08, Henrique Neder <hdneder@ufu.br> wrote:

> From: Henrique Neder <hdneder@ufu.br>
> Subject: st: RES: examples propensity score matching
> To: statalist@hsphsun2.harvard.edu
> Date: Tuesday, October 28, 2008, 2:00 PM
> Ana Gabriela
> 
> Your data have to look like this:
> 	 
>        Year group Varresult1 varresult2 covariate1
> covariate2 ....
> covariatek 
> Obs 1   t1  treat   ....       ....      ....  
> Obs 2   t1  contr
> Obs 3
> 
> .....   t2  treat 
> Obs n   t1  contr 
> 
> Where varresult is result variable and covariate are the
> covariates used in
> logit/probit model.
> 
> If you have no counterfactual information for the period 1
> refering about
> result variables, you can´t estimate double difference but
> you estimate only
> a cross section estimate for the period t2. Your covariates
> in the logit
> model have to be dated in t1 (or more precisely prior to
> treatment). So, if
> your treatment is dated in t1 or before and if you don’t
> observe the control
> individuals in t1, it is impossible to estimate the
> propensity score. You
> have to observe the covariates (used in the logit/probit
> model) prior the
> treatment date unless all your covariates are fixed in
> time.
> 
> Henrique Neder       
> 
> -----Mensagem original----- 
> De: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Em nome de
> Ana Gabriela
> Guerrero Serdan
> Enviada em: terça-feira, 28 de outubro de 2008 16:08
> Para: statalist@hsphsun2.harvard.edu
> Assunto: st: examples propensity score matching
> 
> Dear Stata users, 
> 
> A very basic question. I want to take a look at how to do a
> propensity score
> matching in stata (commands psmatch2, pscore, I think). 
> 
> I have two cross sectional surveys (t1, t2)  where I
> observe treatment and
> control individuals in the second period but I cant know
> the conterfactual
> in t1. I want to use propensity score matching to
> indivudals in t2 to
> individuals in t1 based on some observable characteristics.
> 
> 
> I have technical readings and literature but I would like
> to know the how to
> in Stata. how the data should look? should I pool
> individuals for both
> cross-sections?  
> 
> thanks, 
> Gaby 
> 
> 
>       
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