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Re: st: RE: logistic tranformation, proportion variables


From   Richard Goldstein <richgold@ix.netcom.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: logistic tranformation, proportion variables
Date   Fri, 14 Dec 2007 14:48:32 -0500

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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