I am working with count data and trying to understand if my model fit is acceptable for this poisson Generalized Linear Mixed Model:
Richness.glmer<-glmer(Richness ~ Unit.type + plot.type + (1|NFI.Point), family = poisson, data = PartA.data.Birds )
I ran a dispersion test using overdisp_fun and got the following result:
chisq = 55.90, ratio = 0.65, p = 0.995, logp = -0.00489
With a ratio of 0.65, does this mean my model is acceptable? Or is it underdispersed? I also made the following residual plot of my data, which appears to be okay, but I am not sure if the combination of this residual plot that the 0.65 dispersion ratio indicates a good model fit or not
I understand what I would do if I was running a Generalized Linear Model that had overdispersion issues (which seems to be the most common problem). But in my case with my GLMM I am uncertain of:
1). If my model fit is acceptable, and, if not 2). What to do about it.