All,
As I understand ordered logistic regression, the predictor coefficients (and
odds ratios) are based on the assumption that the pedictor variable has the
same effect (slope) across all categories of the dependendent variable. In the
models I am working with, I do not believe this is a tenable assumption. In
fact, one of my hypotheses is that serious mental illness has a larger effect
in moving a person from drug use to dependence on that drug (categories 2 and
3 for the dependent variable - drug use/dependence) than it does on moving
people from no use to use (categories 1 and 2). For this reason, I have been
using multinomial logistic regression and, in fact, the odds ratios for
serious mental illness and use-dependence are greater than the odds ratio for
SMI and no use - use. My question, after that longish preamble, is can you
compare the odds ratios against each other to see if they are significantly
different? Or equivalently and perhaps more understandably, can you test the
ordered logistic regression assumption that the effect size for a predictor
variable is the same across the ordered levels of the dependent variable?
Thanks for any help!
James
[email protected]
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