[R-sig-ME] Zero variance and Std. Dev. using lmer?

[David Duffy]

On Tue, 13 Jan 2009, Luciano La Sala wrote:

> Dear R-people:
>
> I have run a GLMM (using lmer) with the fixed and random effects detailed
> below. Oddly I think, I get zero variance and Std. Dev. values.
>
> How is that possible? Does it mean that the RE "NestID" is not helping to
> account for autocorrelation among sibling chicks at the nest level?
>
> Or is this a small sample size problem?
>
> model <- lmer(Death10~HO+ClutchSize+SibComp+Yr+(1|NestID),family=binomial,1)
>

Either, I would think.  Have you performed a simple test for extrabinomial
variation? eg Tarone test or Chi-square [latter is just
contingency Chi-square test for NestID x Death10]

David Duffy.
-- 
| David Duffy (MBBS PhD)                                         ,-_|\
| email: davidD at qimr.edu.au  ph: INT+61+7+3362-0217 fax: -0101  /     *
| Epidemiology Unit, Queensland Institute of Medical Research   \_,-._/
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