Question

Suppose you're hiring a new worker for your business. You'd like someone reliable. Suppose you use administer a test to job-seekers many other employers use to determine if applicants have this trait. The test is 90% senstitive and 95% specific. If 60 unreliable people apply and 20 reliable people apply, how many positive results will you have

Answer 1

You will have 21 positive results.

Explanation:

Sensitivity of test:

Is the true positive rate, that is, the proportion of positive results that give positive tests.

Specificity of test:

True negative rate, that is, the proportion of negative results that give negative tests.

90% sensitive, 20 reliable people apply

0.9*20 = 18

95% specific, 60 unreliable people apply

1 - 0.95 = 0.05 of positive results.

0.05*60 = 3

How many positive results will you have?

18 + 3 = 21

You will have 21 positive results.