The CIA and FBI use polygraph machines (lie detectors) to screen job applicants.
ID: 3176625 • Letter: T
Question
The CIA and FBI use polygraph machines (lie detectors) to screen job applicants. A review by a federal panel of scientists reported that "if polygraphs were administered to a group of 10000 people that included ten spies, 1600 innocent people would fail the test and two spies would pass." [Source: Washington Post, May 1, 2006]. A person is selected at random, what is the probability that the person fails the test? Suppose a person fails the test, what is the probability that the person is a spy?Explanation / Answer
as total number of people who falis the test =1600+8=1608
hence probability that person fails the test =1608/10000=0.1608
b)as 8 out of 10 fail the test given they are spy
probabilty that person is spy, given fails the test =8/1608=0.004975