On Mon, 21 Jul 2003 15:01:30 -0400, "Matthew"

> Hi.

> First, I must apologize but I don't have a background in statistical

> analysis. I am reading a paper that is using two models of ordered mutiple

> choice, logit and probit. I know that SPSS can build logit and probit

> models, but are they ordered mutiple choice models? Is there a difference or

> are all logit/probit models actually ordered multiple choice models.

Logit and probit represent continuous distributions.

Their first widespread use, so far as I know, was in

bioassay, where they were used to represent the proportions

of insects (say) that died when given doses of poisons,

or the proportions of mice that were protected by vaccine.

That is a bit different from multiple-choice.

I have thought that "growth" is what the models

are most often representing.

Assuming that your data come in that form,

what do you want to do with ordered multiple categories?

Well, you can *assume* that they came from some

process (of growth; of contagion; whatever) that has

an underlying distribution - and use the corresponding

analysis. The logit (assigning log of P/Q as a criterion)

arises from a wide number of circumstances.

The probit (assigning the Normal z for a proportion)

arises in certain important instances; and it became

the more popular choice 50 years ago, I think, because

folks were already generally accustomed to the "normal"

distribution.

Hope this helps.

--

http://www.pitt.edu/~wpilib/index.html

"Taxes are the price we pay for civilization." Justice Holmes.