Hi all, I was wondering if somebody could give me advice regarding the dispersion parameter in GLMM's. I'm a beginner in R and basically in GLMM's. I've ran a GLMM with a poisson family and got really nice results that conform with theory, as well with results that I've obtained previously with other analysis and that others have obtained in similar studies. But the dispersion parameter is too large (25 compared to 1). So I ran a quasipoisson that allows for overdispersion and all of the significant results fell out. My question is, how much does overdispersion invalidate ones results when using a poisson family? What could the reason be for having non significant results with a quasipoisson distribution? If anybody could give me some help with this or/and recommend me literature that is somewhat comprehensible to lay people (i.e. non statisticians) that would be great. Thanks in advance, Cristina.
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