[R-sig-ME] confusion about lmer output
Douglas Bates
bates at stat.wisc.edu
Tue Mar 8 23:19:25 CET 2011
On Tue, Mar 8, 2011 at 3:06 PM, Sacha Viquerat <tweedie-d at web.de> wrote:
> hello dear mixed effects modeller! i'm a little confused about the output of
> lmer in R. in michael j. crawleys excellent book on R and in various
> examples in the internet, lmer outputs of poisson family models include a
> dispersion factor (as I gather, the scale of the model). well, mine does not
> show this factor:
>
> Generalized linear mixed model fit by the Laplace approximation
> Formula: N_male ~ no3 + (1 | site/sample)
> AIC BIC logLik deviance
> 973.8 987.7 -482.9 965.8
> Random effects:
> Groups Name Variance Std.Dev.
> sample:site (Intercept) 0.12705 0.35644
> site (Intercept) 0.43142 0.65683
> Number of obs: 243, groups: sample:site, 81; site, 27
>
> Fixed effects:
> Estimate Std. Error z value Pr(>|z|)
> (Intercept) 2.2533 0.1434 15.715 < 2e-16 ***
> no3 -0.5861 0.1486 -3.944 8.02e-05 ***
> ---
> Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
> Correlation of Fixed Effects:
> (Intr)
> no3 -0.339
> in all examples i have seen so far, there's usually a useful bit about the
> dispersion of the model like this:
> Estimated scale (compare to 1) 0.9745646
> i strongly suspect this to be due to my version of lmer, right? as a matter
> of fact, my only question would be:
Right.
> how can I tell if my lmer model is overdispersed???
I'll let others more familiar with overdispersion than am I answer that.
> info:
>
> R version 2.11.0 (2010-04-22)
>
> lme4 version 0.999375-38
Both of those are out-of-date. If possible i would recommend
upgrading to R-2.12.2 and to lme4_0.999375-39
>
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