[R-sig-ME] Beta-binomial distributions with lmer?

[Ben Bolker]

  That's a good question, answers will differ.  Since "all models are
wrong" anyway, provided that a mean-variance relationship of V =
phi*N*p*(1-p) seems plausible, I would say you should go for it.  You're
near the cutting edge anyway ... (I don't have a copy, but you might see
whether Zuur et al's book has anything to say on the subject -- they're
very pragmatic ecologists, and I think they use GEE/quasi models quite a
lot ...)

  Ben Bolker


Christine Griffiths wrote:
> Thanks. I was hoping for a miracle that this had been developed within the 
> last couple of months.
> 
> I am on the stats learning curve and am not quite sure how flexible to be 
> with regards to distributions.  Is quasibinomial acceptable, despite having 
> data with a lot of 0s and a lot of 100s?
> 
> Many thanks in advance,
> Christine
> 
> --On 10 June 2009 09:18 -0400 Ben Bolker <bolker at ufl.edu> wrote:
> 
>>   No.  You can use a quasi-binomial model, although
>> the support is a little bit spotty (and beware that
>> quasi- models may falsely report inflation of the
>> random effects).
>>
>>   Ben Bolker
>>
>>
>> Christine Griffiths wrote:
>>> Hi R users,
>>>
>>> Just a query as to whether lme4 can handle beta-binomial distributions
>>> as I  read that this was not available.
>>>
>>> If not, any suggestions on how to handle such a distribution to plot the
>>> following model:
>>> y<-cbind(Biotic,Abiotic)
>>> m1<-lmer(y~Treatment+Month.rain+(1|Month)+(1|Block/EnclosureID/Quadrat))
>>>
>>> y referring to percentage cover of biotic matter.
>>>
>>> Cheers,
>>> Christine
>>>
>>> _______________________________________________
>>> R-sig-mixed-models at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>>
>> --
>> Ben Bolker
>> Associate professor, Biology Dep't, Univ. of Florida
>> bolker at ufl.edu / www.zoology.ufl.edu/bolker
>> GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc
> 
> _______________________________________________
> R-sig-mixed-models at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models


-- 
Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / www.zoology.ufl.edu/bolker
GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc