[R] generalized linear mixed models with a beta distribution

Ben Bolker bolker at ufl.edu
Fri Feb 27 04:12:11 CET 2009

Jeff Evans-5 wrote:
> lme4 does have a leg up on GLIMMIX in other areas, though.
> The latest SAS release (9.2) is now able to compute the Laplace
> approximation of the likelihood, but it will only fit an overdispersion
> parameter using pseudo-likelihoods which can't be used for model
> selection.
> I'm not sure what lme4 is doing differently through the
> quasi-distributions
> that allows this, but it's enormously useful.
> Jeff

Sorry, but I wouldn't necessarily take comfort from this.  I must confess
that I can't keep the distinctions between marginal pseudo/quasi-likelihoods
in my head, but on what grounds are you confident that the number that
lme4 produces can be used for model selection? (I would guess that)
Some people would be happy using QAIC based on pseudo-likelihoods, some
people wouldn't
be happy with anything other than a true likelihood (or approximation

  This discussion is probably better for r-sig-mixed-models ...

  Ben Bolker
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