Dear R users

I am trying to understand how the dispersion parameter in the glmmADBM
package is calculated for the negbin1 family.
Is it correct that the negbin1 family is the same as the quasipoisson
family?
Because when I run a simple model in GLM(family=quasipoisson) or in
glmmADMB(family=negbin) for the Owls-dataset, it gives different dispersion
parameters.

e.g.

ADBM_binom1 <- glmmadmb(NCalls~(FoodTreatment+ArrivalTime)*SexParent+
offset(logBroodSize),
data=Owls,
zeroInflation=FALSE,
family="nbinom1")

Dispersion parameter=8.2014

GLM_quasipois <- glm(NCalls~(FoodTreatment+ArrivalTime)*SexParent+
offset(logBroodSize),
data=Owls,
family=quasipoisson)

Dispersion parameter= 6.259856

Does this mean that the negbin1 and quasipoisson family are not the same?
Or does the glmmADMB package calculates the dispersion parameter in a
different way?

Thank you!

Hanna ten Brink

	[[alternative HTML version deleted]]


