[R-sig-ME] confusion about lmer output
Sacha Viquerat
tweedie-d at web.de
Tue Mar 8 22:06:46 CET 2011
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:
how can I tell if my lmer model is overdispersed???
info:
R version 2.11.0 (2010-04-22)
lme4 version 0.999375-38
More information about the R-sig-mixed-models
mailing list