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From |
"Henrique Neder" <hdneder@ufu.br> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: using pscore and pstest |

Date |
Wed, 23 Apr 2008 09:01:56 -0300 |

Dear Statalists 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 form fweights calculated as the 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 of a previous survey (that is, the second survey was a subsample of the projects of 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 weighted logits 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 logits? 2 - It is adequate to test balance with pstest and pscore without weights and estimate the atts with weights? 3 - I read that a sample proposal are 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 to consider the representation of the program effects in the universe? Best regards Henrique Dantas Neder Universidade Federal de Uberlandia - Minas Gerais - Brazil No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.2/1389 - Release Date: 21/4/2008 08:34 * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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