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Re: st: diagt and accuracy
At 17:23 10/06/2005, Ronan Conroy wrote:
For more about the ROC area, confidence intervals for the difference
between 2 ROC areas for the same disease in the same population, and the
connection with the Mann-Whitney ranksum test, see Newson (2002). This can
be downloaded from my website (see my signature below), either using a
browser or from within Stata by typing
The ROC area is still useful, because it is the Mann Whitney statistic -
the probability that if a person with and a person without the condition
are taken at random, the person with the condition will have the higher
score. In clinical trials, it becomes the probability that a person on the
superior treatment will have a superior response. Both are very useful
Originally I wanted to have ROC area (as calculated in -diagt-), but I was
told that with a dichotomous test ROC area wasn't relevant, ie, I didn't
have different cutpoints at which to operate the test. That's when she
mentioned accuracy defined with prevalence.
In fact, ROC area doesn't account for prevalence either...
and clicking on the hypertext for the paper.
I hope this helps.
Newson R. 2002. Parameters behind "nonparametric" statistics: Kendall's
tau, Somers' D and median differences. The Stata Journal 2(1): 45-64.
Lecturer in Medical Statistics
Department of Public Health Sciences
Division of Asthma, Allergy and Lung Biology
King's College London
5th Floor, Capital House
42 Weston Street
London SE1 3QD
Tel: 020 7848 6648 International +44 20 7848 6648
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or 020 7848 6605 International +44 20 7848 6605
Opinions expressed are those of the author, not the institution.
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