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Re: st: using roctab when lower values of 'classvar' indicate higher risk


From   Ronán Conroy <rconroy@rcsi.ie>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: using roctab when lower values of 'classvar' indicate higher risk
Date   Wed, 28 Mar 2007 20:54:39 +0100

On 27 Márta 2007, at 20:21, Morrison Hodges wrote:

The manual says that when using 'roctab', higher values of 'classvar' must
indicate higher risk. I have data using a cardiac variable called ejection
fraction (EF) as 'classvar', which varies from 0.00 to 1.00, with lower
values indicating higher risk. The 'refvar' is 'status', with 0=alive and
1=dead. The lower the EF the more likely the patient is dead.
Use -logistic- and then -lroc-, which doesn't care which way your predictor variable is scaled.

=========
Ronán Conroy
Royal College of Surgeons in Ireland
rconroy@rcsi.ie
+353 (0) 1 402 2431
+353 (0) 87 799 97 95
http://www.flickr.com/photos/ronanconroy




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