[R] Help re zinb model

blomsp at ozemail.com.au blomsp at ozemail.com.au
Thu Jan 4 07:13:51 CET 2007

Remember that -2 * the difference in the likelihoods between the two models is
asymptotically chi-squared distributed, with degrees of freedom equal to the
difference in number of parameters between the models. So you can just
calculate that for your preferred and null models, then use the pchisq function
to test significance. Get the likelihoods from obj$maxlike.



Philippe Lacherez wrote:
[Hide Quoted Text]
> Hi all,
> I am hoping someone can help with a problem I have. I want to do a
> zero-inflated negative binomial model on some count data.  I have found
> how to get the model (using zicounts), and the test of each predictor on
> both the negative binomial and zero-inflated parts of the distribution.
> Can anyone tell me how I can also get an omnibus test of significance for
> the fit of the model?  Stata I think gives a likelihood ratio chi-square
> test of the full versus null model for the zinb model.  Is there a way to
> get this in R?  Alternatively, is there a way I use the deviance, or
> maximum likelihood value to derive this?
> Cheers
> Philippe Lacherez
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Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
Centre for Resource and Environmental Studies
The Australian National University
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