[R-sig-eco] multiple regression (ONKELINX, Thierry)
Thierry.ONKELINX at inbo.be
Mon Feb 8 17:05:07 CET 2010
Thank you for your comments.
> Interesting thought. Maybe correct. But there are a few
> things to think
> 1. You have to assume that sampling was such that all species
> out there have ended up in the data. Formulated
> differently...you need to know the N_i (maximum number of
> possible species) in the B(p_i,N_i).
I assume that one knowns all species that could occur in the region.
That is not the same as all samples species.
> 2. Not sure how the variance structure would work out;
> Poisson or NB versus Binomial. I guess it may work out ok.
> 3. B(p_i,N_i) means N_i independent (!) trials, each (!)
> with probability p_i of success. But what happens if these
> trials (=species) are not independent?
Agreed that this might be problematic. But isn't this also a problem
with a Poisson model? Since you assume that the number of species only
depends on the covariantes and not on the presence of some species?
> Anyway....it is not my problem....but you would need to think
> about these things.
I was replying to a question. So it is is my problem neither ;-) Or are
least not at present, as I might get similar datasets in the future.
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