[R-sig-ME] Overdispersion lme4 binomial

[Chris Mcowen]

Dear List,

I am wanting to test for overdispersion in my model and am unsure how for my specific case.

I have 2 random factors, 7 fixed factors that have multiple levels and are categorical and then i have a binary response (True or False).

model1 <- lmer(threattf~1+(1|order/family) + geophyte + seasonality + pollendispersal + breedingsystem*fruit + habit + lifeform + woodyness, family=binomial)

I would be very grateful if somebody could point me in the right direction for testing for overdispersion under such scenarios?

Please see part of the output below -

Thanks for any help, and if more data is required feel free to ask.

Chris

Generalized linear mixed model fit by the Laplace approximation 
Formula: threattf ~ 1 + (1 | order/family) + geophyte + seasonality +      pollendispersal + breedingsystem * fruit + habit + lifeform +      woodyness 
  AIC  BIC logLik deviance
 1562 1649 -764.2     1528
Random effects:
 Groups       Name        Variance Std.Dev.
 family:order (Intercept) 0.26932  0.51896 
 order        (Intercept) 0.00000  0.00000 
Number of obs: 1242, groups: family:order, 43; order, 9

Fixed effects:
                       Estimate Std. Error z value Pr(>|z|)   
(Intercept)            -0.10413    0.98004  -0.106  0.91538