Hi Sam,

I'm pretty sure GLMMs assume equal variances for all levels of the random
effects.

If you want to know intraindividual variability in a trait, though, Stamps,
Briffa and Biro just published "Unpredictable animals: individual
differences in intraindividual variability (IIV)" in the most recent Animal
Behaviour, and that seems to be what you want.

Cheers

aj


On Mon, Jun 18, 2012 at 9:29 AM, Samantha Patrick <spatrick@cebc.cnrs.fr>wrote:

> Hi
>
> I am currently trying to estimate how consistent individuals are in a
> trait.  I want to produce an estimate of the variability for each level of
> a random effect (ID).  I can do this simply by calculation the variance for
> each ID separately but I am trying to extract this information from a mixed
> model (either in lmer or mcmcglmm).  I have trawled the mailing list but
> can not find any answers.
>
> As an simplified dummy example I have 2 individuals, each with 5
> observations of a trait.  I can calculate 2 variances, using the 5
> observations for each individual.
>
> head(Data)
> ID    trait1
> 1        10
> 1        15
> 1        12
> 1        19
> 1        11
> 2        9
> 2        10
> 2        9
> 2        10
> 2        10
>
> Variance for 1 = 4.67
> Variance for 2 = 0.3
>
> Alternatively I can fit a model of:
>
> model1<-lmer(trait1 ~(1|ID))
>
> From the variance covariance matrix I can easily extract the between and
> within group variances, but is there a way to extract individual variance
> estimates?
>
> Many Thanks
>
> Sam
>
> --
>
> Dr Samantha Patrick
> Post Doctoral Fellow
> Centre d'Etudes Biologiques de Chizé - CNRS
> 79360 Villiers-en-Bois
> France
> T:+33 549 097 846
> M:+33 675 603 451
> Skype: sammy_patrick
> http://www.cebc.cnrs.fr/**Fidentite/patrick/patrick.htm<http://www.cebc.cnrs.fr/Fidentite/patrick/patrick.htm>
> http://www.researchgate.net/**profile/Samantha_Patrick/<http://www.researchgate.net/profile/Samantha_Patrick/>
>
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> https://stat.ethz.ch/mailman/**listinfo/r-sig-mixed-models<https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models>
>



-- 
Alecia Carter
Large Animal Research Group
Department of Zoology
University of Cambridge
Downing Street
Cambridge
CB2 3EJ
E: ac854@cam.ac.uk
https://sites.google.com/site/aleciajcarter/home

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