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Date:         Fri, 23 Sep 2005 07:07:48 -0400
Reply-To:     John Painter <painter@email.unc.edu>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         John Painter <painter@email.unc.edu>
Subject:      Re: Propensity score matching
Comments: To: Alice Sullivan <A.Sullivan@ioe.ac.uk>
In-Reply-To:  <DDEFF61292422A4A9B8EF93B3D11BBDD90A72E@bgmail01.ioead>
Content-Type: TEXT/PLAIN; charset=US-ASCII

Hello,

There is a SPSS program for propensity matching at my web site: www.unc.edu\~painter

~ John Painter

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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