Re: st: RE: logistic tranformation, proportion variables

[Richard Goldstein <richgold@ix.netcom.com>]

A couple of comments about Jay's material below (some has been snipped):

1. Yes, Aitchison wrote an important book; users should note, however, 
that there was a big controversy over this in the 1980's in Geology 
between Aitchison and GM Philip/DF Watson. I have not delved into this 
in sufficient detail to have an opinion on whether Aitchison was correct.

Regarding the Smithson/Verkuilen paper, note, if you try to match their 
results (as I did), that they used one-sided p-values (I checked this 
with Smithson and he agreed that they had).

Rich

Verkuilen, Jay wrote:
[snip]

> Some points:
>
> (1) There is a very large literature in geostatistics on proportions
> data summarized in the excellent book by John Aitchison, Compsitional
> Data Analysis. The zeros problem is, of course, a real issue and this
> literature has dealt with the problem to some degree. There are a few
> articles by econometricians that might be of use to you. The references
> are in the 2003 edition of Aitchison's book (which was originally
> published in 1986). http://en.wikipedia.org/wiki/Compositional_data
>
> (Shameless self-promotion: The next two points involve work I'm
> currently engaged in.) 
> (2) Michael Smithson of ANU and I published an article on using beta
> regression for these kinds of data published last year in Psychological
> Methods (the APA's methodology journal). It can be found here:
> http://psychology.anu.edu.au/people/smithson/details/betareg/betareg.htm
> l We talk about the zeros problem quite a bit, though see below.
> Independently Maarten Buis wrote some Stata software that estimates this
> model. If you have need of mixed model analysis, contact me as Mike and
> I have worked out the details and, indeed, use some data very much like
> your own as a test case that Mike got from an economist friend of his at
> ANU. We are in the process of writing this paper up but it's really not
> ready for readers or I'd send it to you. 
[snip]
> Jay
> --
> J. Verkuilen
> Assistant Professor of Educational Psychology
> City University of New York-Graduate Center
> 365 Fifth Ave.
> New York, NY 10016
> Email: jverkuilen@gc.cuny.edu
> Office: (212) 817-8286 
> FAX: (212) 817-1516
> Cell: (217) 390-4609
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