Re: st: using pscore and pstest

[Steven Samuels <sjhsamuels@earthlink.net>]

-
Henrique, how were the program and beneficiary sub-samples selected?  
Are the beneficiary and control sampling units projects or   
households?  Was there control of the number of the beneficiary and  
control units--for example to achieve approximately equal numbers, or  
minimum numbers of each?

-Steven
On Apr 24, 2008, at 8:32 PM, Henrique Neder wrote:


> Dear
> I have a problem with the use of the pscore and pstest commands. My  
> sample
> is a cluster sample in that the sample observations are selected by  
> the
> followings steps:
>
> 1 - The survey is made in five States and in each State we selected  
> some
> number of projects (the primary sample units - PSUs) in all sub- 
> regions of
> this State.
>
> 2 - In each project we selected a fixed number of households.
>
> The sample weights are of the fweights form, calculated as the  
> ratio  -
> number of households in each sub-region (universe) / the number of
> households (observations) selected in the sample and inside that same
> sub-region. Alternatively, we have a pweight, because the projects  
> were
> selected with PPS (with probability proportionate to the number of the
> households in each project in the universe). This sample of  
> projects were
> selected as a sub-sample of the projects in a previous survey (that  
> is, the
> second survey was a subsample of the projects in the first survey).
> We have in the survey two subsamples: a sub-sample of a program
> beneficiaries and a control sub-sample.
>
> I executed the commands pstest and pscore using a logit model with  
> y = dummy
> of participation program and yi (covariates) = variables that  
> explain the
> participation. In the first execution I executed the commands with
> propensities scores obtained through non weighted logit regressions  
> and some
> models are balanced in the pstest and pscore commands. But when I  
> use the
> weighted logits, the balancing tests are not satisfied (the pscore  
> command
> stops and in the pstest the covariates are unbalanced with small p- 
> values
> and the conjoint chi-square test with low p-value, too).
>
> My questions are:
>
> 1 - It is necessary to execute the commands with propensities scores
> obtained through weighed logit regressions to estimate the atts?
>
> 2 - It is adequate to test balancing with pstest and pscore without  
> weights
> and estimate the atts with propensities scores obtained through  
> weighted
> logit regressions?
>
> 3 - I read that a sample proposal is to weight the treated  
> observations with
> the weight = 1 / propensity and the untreated with the weight = 1/(1 -
> propensity).  In my case, is this solution appropriate? Does it  
> correct the
> estimates considering the representation of the program effects in the
> universe?
>
> Best regards
>
> Henrique Dantas Neder
> Universidade Federal de Uberl�ndia - Minas Gerais - Brazil
>
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