Re: propensity score for 3 treatments

Posted by Maguin, Eugene on Nov 30, 2012; 3:11pm
URL: http://spssx-discussion.165.s1.nabble.com/propensity-score-for-3-treatments-tp5716540p5716546.html

I first thought of an ordinal regression but then realized that there is no assurance that the parallel lines assumption would be met and then switched to multinomial regression. Maybe this is not a problem but the usual propensity setup has matching on the computed logit or log odds value from a logistic regression with a dichotomous DV. But with a three category DV you get two computed logits or log odds values irrespective of whether you use ordinal or multinomial. So how is the matching to be done.

You've got to figure that this problem has come up before and an accepted method has been developed; however, I don't know what it is. My suggestion is to average the logits and match on that (but check the resulting match to see how well the match is on each logit value). My rationale is that if you formed matched triplets and assigned them to condition then did the multinomial regression analysis, each member of the triplet would have the same average logit and logit components.

Gene Maguin

-----Original Message-----
From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Bruce Weaver
Sent: Friday, November 30, 2012 9:39 AM
To: [hidden email]
Subject: Re: propensity score for 3 treatments

Multinomial logistic regression (NOMREG)?



la volta statistics wrote

> Hi all
>
> To control for confounding bias from non-random treatment assignment
> with
> 3
> different treatments, I would like to calculate a propensity score I
> later can use in a cox regression model. I know the procedures for a
> two-treatment approach (logistic regression). But how would I
> calculate such a score when I have three treatments?
>
>
>
> Thanks in advance
>
> Christian
>
>
>
>
>
> **********************************
> la volta statistics
> Christian Schmidhauser, Dr.phil.II
> Weinbergstrasse 108
> CH-8006 Zürich
> Tel: [phone]
> Fax: [phone]
> email:  <mailto:

> schmidhauser@

> > mailto:

> schmidhauser@

>
> Web:  <http://www.lavolta.ch> www.lavolta.ch





-----
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Bruce Weaver
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