[EMAIL PROTECTED] wrote:
I recall a concept of Snout: sensitivity that is high enough to essentially
rule out the presence of disease. And Spin: specificity that is high enough
to essentially rule in the presence of disease.
So perhaps the below is backwards? The higher the sensitivity, the greater the NPV? And the higher the specificity, the
greater the PPV?
Why should we care when we can directly estimate Prob(disease | test
results and risk factors)? Am I the only person who likes logistic
regression models this week?
Frank
http://www.musc.edu/dc/icrebm/diagnostictests.html
--Chris Ryan
---- Original message ----
Date: Mon, 13 Oct 2008 18:14:39 -0400
From: "John Sorkin" <[EMAIL PROTECTED]>
Subject: Re: [R] Fw: Logistic regresion - Interpreting (SENS) and (SPEC)
To: "Ph.D. Robert W. Baer" <[EMAIL PROTECTED]>, "Frank E Harrell Jr" <[EMAIL PROTECTED]>
Cc: r-help@r-project.org, [EMAIL PROTECTED], [EMAIL PROTECTED]
. . . . .
Further, PPV is a function of sensitivity (for a given specificity in a
population with a given disease prevalence), the higher the sensitivity almost
always the greater the PPV (it can by unchanged, but I don't believe it can be
lower) and as
NPV is a function of specificity (for a given sensitivity in a
population with a given disease prevelance), the higher the specificity almost
always the greater the NPV (it can by unchanged, but I don't believe it can be
lower) . . . .
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--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
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