Hi Team,

I'm currently trying to calculate repeatability of a behaviour from a
poisson GLMM using Nakagawa & Schielzeth's (2010 Biological Reviews)
repeatability point estimates. With multiplicative overdispersion [in
lmer()] I have to estimate the dispersion parameter to calculate the point
estimate. For a GLM something like this is apparently ok:

df<-(n-nparameters-1)
omega<-(sum(residuals(M1)^2))/df

but this doesn't apply to GLMMs as calculating the df is tricky (given the
parameters [unaccounted for] in the random effects: Bolker et al 2009 TREE).

My question is thus: does anyone know how to calculate the dispersion
parameter for a (poisson) GLMM?
Thanks in advance for your help,

aj

-- 
Alecia Carter
PhD Scholar

Fenner School of Environment and Society
ANU College of Medicine, Biology & Environment
W.K Hancock Building [43]
The Australian National University
Canberra ACT 0200 Australia
T: + 61 2 6125 1127
F: + 61 2 6125 0757
E: alecia.carter@anu.edu.au
http://fennerschool.anu.edu.au/people/alecia-carter

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