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 <[email protected]> wrote:
> From: Henrique Neder <[email protected]>
> Subject: st: RES: examples propensity score matching
> To: [email protected]
> 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: [email protected]
> [mailto:[email protected]] Em nome de
> Ana Gabriela
> Guerrero Serdan
> Enviada em: terça-feira, 28 de outubro de 2008 16:08
> Para: [email protected]
> 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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