120 likes | 220 Views
Lesson #10 Screening Tests. D D’. TP. +. FP. FN. -. TN. = P( + | D ). Sensitivity = Se. = P( - | D’ ). Specificity = Sp. 95. 20. 5. 180. Ca no Ca. +. -. 100 200. Se. = .95. Sp. = .90. 95. 200. 5. 1800. Ca no Ca. +. -. 100 2000.
E N D
Lesson #10 Screening Tests
D D’ TP + FP FN - TN = P( + | D ) Sensitivity = Se = P( - | D’ ) Specificity = Sp
95 20 5 180 Ca no Ca + - 100200 Se = .95 Sp = .90
95 200 5 1800 Ca no Ca + - 1002000 Se = .95 Sp = .90
Positive Predictive Value (PPV) PPV = P( D | + ) Not the same as Se!
The simplest form of Bayes’ Theorem is: PPV = P(D | +)
Se p 1-Sp 1-p PPV = P(D | +)
PPV Se = .95 Sp = .90 p = .02 = .162
Ca no Ca 95 95 200 20 + 5 5 1800 180 - 100200 Ca no Ca + - 1002000
+ P(Ca and +) = P(TP) Se = .95 = (.02)(.95) = .019 Ca .05 .02 - P(+) = .117 + .98 P(No Ca and +) = P(FP) .10 = (.98)(.10) = .098 No Ca Sp = .90 -