Hello,

I am modelling in glmmADMB count data (I´m using a negative binomial
distribution to avoid possitive overdispersion) with four fixed and one
random effect. I´m also using MuMIn package to calculate the AICc and also
to model averaging using the function dredge. What I do not understand is
why dredge calculates a different value of the AICc and degrees of freedom
than the function AICc (please see bellow). Also the logLik changes (as
expected).

> logLik (glmmadmb.Tot.Pr.nb) ---- 12 in model selection table
'log Lik.' -379.739 (df=6)
> logLik (glmmadmb.Tot.P.nb)------ 16 in model selection table
'log Lik.' -379.688 (df=7)

                            df     AICc
glmmadmb.Tot.Pr.nb  6   772.8113----12 in model selection table
glmmadmb.Tot.P.nb   7   775.1825---- 16 in model selection table


Model selection table
     (Int)      Agr/100 Brd/100 Frs/100  HD/100 df   logLik  AICc delta
weight
12 0.90850 -10.570   17.08               1.4220  5 -397.992 806.9  0.00
 0.713
16 1.10300 -10.470   17.39 -0.7603   1.5140   6 -397.730 808.8  1.87  0.280


Can anyone explain me why this happend? and which values are correct, those
from dredge function or those from AICc function?

Thank you very much in advace.

Carlos

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