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R-sig-Epi Digest, Vol 41, Issue 1

Ol? Mirian,

Are you using Poisson models with an offset?  I've never tried this  
with the Epi package so giving us some sample code and sample data  
structure would help.

But if you simply use glm, one way to account for over-dispersion is  
by specifying family=quasipoisson.  It maximizes the quasilikelihood  
rather than the likelihood (don't ask me the maths of this, maybe  
start with the Wikipedia...).

Another approach might be hierarchical modelling but we'd need to know  
your data structure.

Cheers.

David Evans
-----------------
Epidemiologist, Kappa Sant?