Hello, 

I have a question for conducting a GLMM with the Poisson distribution. I ran the following command:

Mglmm1<-lmer(Richness ~ 1 + NAP + fExp + (1 | fBeach), family=poisson(link="log"),data=RIKZ)
summary(Mglmm1)

However, in the summary output does not provide the null and residual deviances to determine wether overdispersion has occurred. How can I calculate these values given the model output below?

Thank you very much in advance!

Zofia

PhD. Candidate McGill University
Department of Biology
1205 Avenue Docteur Penfield
Montreal, QC, H3A 1B1
Phone (514) 398-4119

Output:

Generalized linear mixed model fit by the Laplace approximation 
Formula: Richness ~ 1 + NAP + fExp + (1 | fBeach) 
   Data: RIKZ 
   AIC   BIC logLik deviance
 71.56 78.78 -31.78    63.56
Random effects:
 Groups Name        Variance Std.Dev.
 fBeach (Intercept) 0.060445 0.24586 
Number of obs: 45, groups: fBeach, 9

Fixed effects:
            Estimate Std. Error z value Pr(>|z|)    
(Intercept)  2.04181    0.13302  15.350  < 2e-16 ***
NAP         -0.50383    0.07421  -6.789 1.13e-11 ***
fExp11      -0.86703    0.22353  -3.879 0.000105 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Correlation of Fixed Effects:
       (Intr) NAP   
NAP     0.065       
fExp11 -0.595 -0.044







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