Have run a glm with Poisson-distributed errors on count data with 6 treatments and control. The output shows Residual deviance is 96.5 on 91 degrees of freedom, and result of:
1 - pchisq(summary(model.pois)$deviance, summary(model.pois)$df.residual)
is 0.33, so non-significant. I wanted to look at overdispersion using
AER package, but had issues loading the package, so couldn't run it.
However, my data is full of 0s (37/98 samples) and I expected I'd have to run a zero-inflated model. The poisson showed distribution is OK, so unless I've done something wrong, is there any need to run a zero-inflated model?