st: Polytomous vs "regular" unconditional logistic regression

[Roger Milne <rlm@unimelb.edu.au>]

Hi,

I don't understand why I get different estimates (ignoring standard errors) 
from the following two models:

1. Multivariate polytomous logistic regression, with outcome categories 0, 
1 and 2 (with ", basecategory(0)")
2. Two separate multivariate (same covariates) "regular" logistic 
regression models:
        (i)  with ", if outcome~=2"
        (ii) with ", if outcome~=1"

The "coeff" estimates are very different (eg.  -1.52 vs. -1.06)

For the univariate case, I get the same estimates from 1 and 2, but they 
start to "diverge" as soon as I add an additional covariate.

Thanks,

Roger Milne.

Roger Milne
Research Fellow
Centre for Genetic Epidemiology
University of Melbourne
Tel:  +613 8344 0803
Fax: +613 9349 5815
email: rlm@unimelb.edu.au

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