In: Statistics and Probability
At a large factory 1% of the workers are using drugs, an event we’ll call D. An employee has just been tested by a procedure that has a 3% false positive rate and has failed the test, F. Assume that the test is always positive for people who are using drugs. (i) Find P(D|F). (ii) Suppose that the employee failed the first test (F1). What is the probability he will fail the second test (F2), i.e., compute P(F2|F1). (iii) What is the probability he is using drugs if he fails both tests, i.e., P (D|F1 ∩ F2).