Hi,
I am running a poisson regression, but if I run a cox regression and
use the same covariates, then some of the rate ratios clearly differ
between the models. I always thought that a cox regression should give
approx. the same results as a poisson regression. What could be the
reason for this?
In more detail:
I first stset with age as time:
.stset dox, fail(fail) enter(doe) origin(dob) id(id)
then I used stsplit to create age and calender period bands and used
poisson regression with additional covariates (sex, age at diagnosis,
treatment etc)..
then, as a check and out of curiousity I ran a cox regression model,
but the rate ratios for treatment and in particular for age at
diagnosis differ between the models.
Thanks for your help.
Raoul
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