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Re: st: poisson regression predicted values
Richard Goldstein wrote:
I have estimated a poisson regression (includes some interaction terms
and uses cluster SE's). After estimation I obtained predicted values
(-predict newvar, ir-) and some of the IR's are greater than 1.0
(Similarly, using -predict newvar- gives some counts that are greater
than the exposure (or denominator).) I have not known this to occur
before and have the following questions:
1. is this a serious problem?
No, it isn't a problem.
An incidence rate can take any non-negative value; it is the number of
events divided by the time at risk (the "exposure" in poisson regression
terms). So obviously the numerical magnitude of an incidence rate
depends on the time unit chosen (seconds, years, centuries).
Hope this helps
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