[R-sig-ME] Scale parameter and within variance random factor in a poisson model

Renwick, A. R. a.renwick at abdn.ac.uk
Fri Sep 19 12:59:02 CEST 2008

Dear All
Sorry but I have another question!
I am running a GLMM with poisson distribution and log link and I was wondering:
1) how to get the scale parameter and if there is a reason why the new version of lme4 does not report that in the model summary
2) why GLMM models do not give the within variance of the random factor.  When using a poisson family the value for sigma using the VarCorr(model) command is not estimated , probably due to the fact that REML criterion is not defined for generalized linear mixed models.  One way I thought to obtain this within variation was to calulate it using the ST value (ST=variance between/ variance within) and I was wondering if this is the correct procedure or if there is a better method.

Many thanks again,


Anna Renwick
Zoology Building
School of Biological Sciences
University of Aberdeen
AB24 2TZ

The University of Aberdeen is a charity registered in Scotland, No SC013683.

More information about the R-sig-mixed-models mailing list