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st: RE: gpscore for propensity score of 4 observed groups

 From "Villa Lora, Juan Miguel" To "statalist@hsphsun2.harvard.edu" Subject st: RE: gpscore for propensity score of 4 observed groups Date Tue, 12 Oct 2010 17:26:56 -0400

```Hey Stephen!
Before answering your question I'd like to understand your treatment variable. You are stressing that you got four different groups, which makes me think that you are dealing with a categorical variable instead of a continuous variable as it's required for gpscore. Remember that Hirano and Imbens (2005) spell out that this treatment variable must be a normal distributed (one of the basic assumptions of the analysis).  Are you sure your treatment variable is continuous?
Juan
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of oconnor7@u.washington.edu [oconnor7@u.washington.edu]
Sent: Tuesday, October 12, 2010 5:15 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: gpscore for propensity score of 4 observed groups

Hi,

I have technical question regarding gpscore.

If my treatment variable is type of injury severity, what should I put for "cutpoints", "index", and "nq_gps"? The treatment level has four different levels of injury severity.

What I am seeking is to create a propensity score for the likelihood that a person develops a certain type of injury, in this case TBI, based upon a list of covariates.

This is the syntax I used for a preliminary analysis:

gpscore  age child_gender prev_anxiety prev_depn prev_adhd prev_behavioral prev_other_mh, t(inj_severity) gpscore(mygps) predict(hat_inj_sev) sigma(hat_sd) cutpoints (inj_severity) index(p50) nq_gps(4)

Again, I am unsure of cutpoints, index, and nq_qps given that I have four established groups for the treatment variable.

Thank you,
Stephen

Stephen O'Connor
Senior Fellow
Harborview Injury Prevention & Research Center
Department of Psychiatry & Behavioral Sciences
University of Washington at Harborview Medical Center

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