4
$\begingroup$

I am in the process of conducting zero-inflated generalised mixed effects models with Poisson distributions and have been using the testDispersion() function of the DHARMa package in R to determine if my data is significantly over/underdispersed. Whilst this function does provide a p-value to indicate significance of the dispersion I was wondering if there was a particular dispersion ratio above or below 1 that is used to recommend using a different distribution (e.g. negative binomial) to account for the dispersion.

$\endgroup$

1 Answer 1

3
$\begingroup$

No, there is no universal rule of thumb for this, and you should definitey not rely on p values. If you have reason to think that you have over or under dispersion, then go ahead and fit a model that accounts for this and compare the model fit with the Poisson model.

$\endgroup$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.