Post-Test Probability

Problem

Return the post-test probability after a positive test: multiply the pre-test odds prevalence/(1-prevalence) by the positive likelihood ratio and convert the result back to a probability. Return 0.0 when prevalence is outside (0, 1) or specificity >= 1.

Hint

Odds in, likelihood ratio scaling, probability out.

Test cases

case 1

in: [0.1,0.9,0.8]

expected: 0.3333333333333334

case 2

in: [0.5,0.5,0.5]

expected: 0.5

case 3

in: [0.01,1,0.95]

expected: 0.1680672268907562

case 4

in: [0.2,0.8,1]

expected: 0

case 5

in: [0,0.9,0.8]

expected: 0

Starter codePython

def post_test_probability(prevalence, sensitivity, specificity):
    # Your code here
    pass

5 test cases · run your code against them in the editor