[R] How to tell if there is overdispersion in a GLMM?

[maggy yan]

I read something on http://glmm.wikidot.com/faq, under "How can I deal with
overdispersion in GLMMs?":

library(lme4)  ## 1.0-4set.seed(101)
d <- data.frame(y=rpois(1000,lambda=3),x=runif(1000),
            f=factor(sample(1:10,size=1000,replace=TRUE)))
m1 <- glmer(y~x+(1|f),data=d,family=poisson)
overdisp_fun(m1)##        chisq        ratio          rdf            p
## 1026.7780815    1.0298677  997.0000000    0.2497659
library(glmmADMB)  ## 0.7.7
m2 <- glmmadmb(y~x+(1|f),data=d,family="poisson")
overdisp_fun(m2)##        chisq        ratio          rdf            p
## 1026.7585031    1.0298480  997.0000000    0.2499024

In both case, the chisq is > rdf, does it mean there is over dispersion?

thanks for any help

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