a) Assuming one of the subjects is chosen randomly, the probability that the test result is a false positive is 6/23.
b) 6 potential employees will suffer from a false positive result because they do not use drugs but the test results show they do.
A false positive is a result that shows something to be true when it is false.
Pre-Employment Drug Screening Results
Positive Test Result Negative Test Result
(Test shows drug use) (Test does not show)
Subject uses drugs 17 15
Subject does not use drugs 6 84
Total number of subjects who use drugs = 32 (17 + 15)
Total number of subjects who do not use drugs = 90 (6 + 84)
The number of subjects who use drugs with positive results = 17
The number of subjects who do not use drugs with positive results = 6
The number of subjects who use drugs with negative results = 15
The number of subjects who do not use drugs with negative result = 84
The probability that the test result is a false positive = 6/23