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Re: st: NBREG for ordinal scales

From   David Bell <>
Subject   Re: st: NBREG for ordinal scales
Date   Wed, 11 Oct 2006 15:47:41 -0400

On Oct 10, 2006, at 1:08 PM, n j cox wrote:

I think it's pretty much wired in that Poisson,
negative binomial, etc., really are for counts.

Actually, I seem to recall that Poisson processes are based on probabilities of changes of state. If you are counting the sequential changes, then you have count data and it is straightforward to label each state with the number of persons (or other entities) the state represents. If, on the other hand, the changes are psychological (such as the change from being strongly opposed to some action to being "only opposed") then the labels for the states are not counts. As I recall, James Coleman, in Introduction to Mathematical Sociology (1965) used Poisson models of responses to ordinal attitudinal scales.

The approach never became popular in sociology, but it gives a justification for using Poisson and related processes on non-count data, as Matthew seems to want to do.

David C. Bell
Indiana University Purdue University Indianapolis (IUPUI)

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