```Date: Fri, 23 Sep 2005 07:39:52 -0400 Reply-To: John Painter Sender: "SPSSX(r) Discussion" From: John Painter Subject: Re: Propensity score matching Comments: To: Alice Sullivan In-Reply-To: Content-Type: TEXT/PLAIN; charset=US-ASCII Here is a list of references you might find useful: http://sswnt5.sowo.unc.edu/VRC/Lectures/PSM_references.pdf good luck, John On Fri, 23 Sep 2005, Alice Sullivan wrote: > Hi, > > > > I am doing an analysis of academic outcomes for children in private and > state schools, and am trying to use the propensity score approach. > > > > I want to match on the exact propensity score, dropping unmatched cases > from the sample. I did try the binning approach, but since my dataset is > large (more than 10,000 cases), it was impossible to balance the bins. > > > > I have calculated the propensity score using 'save predicted values - > probabilities' in binary logistic regression, with the 'treatment' > (state/private school) as the dependent variable, and a set of > predictors (social class, etc), as follows: > > > > LOGISTIC REGRESSION private > > /METHOD = ENTER region3s faclas7m educatio famtrad kidno mobooks moint > Zabilit11 teacha_1 teachmiss abilmiss > > /CONTRAST (region3s)=Indicator /CONTRAST (faclas7m)=Indicator > /CONTRAST (educatio)=Indicator /CONTRAST > > (famtrad)=Indicator /CONTRAST (kidno)=Indicator /CONTRAST > (mobooks)=Indicator /CONTRAST (moint)=Indicator /CONTRAST > > (abilmiss)=Indicator /CONTRAST (teachmiss)=Indicator > > /SAVE = PRED > > /CRITERIA = PIN(.05) POUT(.10) ITERATE(20) CUT(.5) . > > > > My problem is that the number of values I get from this is huge - it > exceeds 1000, so I can't even run a crosstabs. I can run a table of > frequencies, but it's too huge to print out. > > > > My questions are: > > 1. Am I doing something wrong? > 2. Is it acceptable to group the propensity scores together - e.g. > into percentiles or deciles, before dropping unmatched cases, or would > this defeat the object? > 3. Has anyone written syntax to identify/drop unmatched cases? > (Doing it by hand is a daunting task with so many values!). > > > > Many Thanks, > > Alice > > > > > > Dr. Alice Sullivan > > Centre for Longitudinal Studies > > Institute of Education > > 20 Bedford Way > > LONDON > > WC1H OAL > > > ```

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