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Re: st: ROC curve for ordinal data


From   Ronan M Conroy <rconroy@rcsi.ie>
To   "statalist hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: ROC curve for ordinal data
Date   Fri, 19 Dec 2003 14:37:14 +0000

on 19/12/2003 08:32, fmedeiros at fmedeiros@uol.com.br wrote:

> Is there a minimum number of categories to adequately fit a
> parametric ROC curve for ordinal data? For example, can we
> adequately fit a model when we have only 3 categories (for
> instance, abnormal, borderline and normal)

You could try -nproc- by Philip Price and Fred Wolfe. But with so few
categories, you would be better off looking at the performance of individual
cutoff points on the scale in terms of sensitivity, specificity, positive
and negative predictive values. The ROC area is a very broad brush, and does
not assess the suitability of a test for specific purposes.

Ronan M Conroy (rconroy@rcsi.ie)
Lecturer in Biostatistics
Royal College of Surgeons
Dublin 2, Ireland
+353 1 402 2431 (fax 2764)

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