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st: poisson regression predicted values


From   Richard Goldstein <richgold@ix.netcom.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: poisson regression predicted values
Date   Wed, 05 Oct 2005 13:01:23 -0400

Dear listers:

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?

2. (esp. if answer to 1 is "yes") -- what might cause this and, therefor, what can I do about it?

Thanks,

Rich Goldstein

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