[R-sig-ME] lme4, lme4a, and overdispersed distributions (again)

Jeffrey Evans Jeffrey.Evans at dartmouth.edu
Thu Jun 24 18:54:23 CEST 2010

Like others, I have experienced trouble with estimation of the scale
parameter using the quasi-distributions in lme4, which is necessary to
calculate QAICc and rank overdispersed generalized linear mixed models. 

I had several exchanges with Ben Bolker about this early last year after his
TREE paper came out
19-6), and I know it's been discussed on on this list. Has there been or is
there any potential resolution to this forthcoming in future releases of
lme4 or lme4a? I run into overdispersed binomial distributions frequently
and have had to use SAS to deal with them. SAS appears to work, but it won't
estimate the overdispersion parameter using laplace estimation (only PQL),
As I understand it, these pseudo-Iikelihoods can't be used for model
ranking. I don't know why SAS can't/won't, but lme4 will run these
quasi-binomial and quasi-poisson distributions with Laplace estimation.

Is there a workable way to use lme4 for modeling overdispersed binomial

Thanks again,

Jeff Evans
Dartmouth College

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