Statalist The Stata Listserver


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

Re: st: NBREG for ordinal scales


From   "David Barron" <mothsailor@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: NBREG for ordinal scales
Date   Thu, 12 Oct 2006 08:46:21 +0100


If, in fact, the DV has a Poisson or negative binomial distribution,
then that is your justification for using count models.  But how do
you know that it does have such a distribution???  And why would you
even think that it does, given the way the questions are worded?  Is
there some "classic" piece these authors cite, or do they just do it
without citation?  There must have been somebody who started this -
if you could find out who it was that might help solve the puzzle.

But of course data of this form cannot possibly have a Poisson or
negative binomial distribution because, as somone has already pointed
out, these distributions are unbounded on the right, while the ordinal
scales being talked about only take a few values.   This is quite
apart from thinking about the random process that generates the
observed data in the first place.  I would imagine that the Poisson or
neg bin might be a reasonable approximation in some situations, but if
expected values are toward the upper end of the range of values then
they can't possibly be.

I don't really undestand why one would want to use these methods when
apparently superior alternatives (such as ordinal logit) exist.

--
=================================
David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index