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? 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) . . . . ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
