[R] Assessing overdispersion and using quasi model with lmer, possible?

Ben Bolker bbolker at gmail.com
Fri Oct 19 14:28:08 CEST 2012

swertie <v_coudrain <at> voila.fr> writes:

> I am trying to model data on species abundance (count data) with a poisson
> error distribution. I have a fixed and a random variables and thus needs a
> mixed model. I strongly doubt that my model is overdispersed but I don't
> know how to get the overdispersion parameter in a mixed model. Maybe someone
> can help me on this point. Secondly, it seems that quasi models cannot be
> implemented with the function lmer, is there an option? If not, I certainly
> should go to variable transformation and use a gaussian error distribution,
> but it is not optimal.

  You should read the section in http://glmm.wikidot.com/faq on
overdispersion, and address further questions to the
r-sig-mixed-models <at> r-project.org mailing list ...

  Ben Bolker

More information about the R-help mailing list