Lie detectors are controversial instruments, barred from use as evidence in many courts. Nonetheless, many employers use lie detector screening as part of their hiring process. There has been some research, but no agreement, about the reliability of polygraph tests.

Based on this research, suppose that a polygraph can detect 65% of lies, but incorrectly identifies 15% of true statements as lies.

The company gives everyone a polygraph test, asking

“Have you ever stolen anything from your place of work?”

Naturally, all the applicants answer “No,” but the company has evidence to suggest that 5% of the applicants are lying.

When the polygraph indicates that the applicant is lying, that person is ineligible for a job.

a) Here is the outline of a probability tree for this situation.
Fill in the probabilities

b) What is the probability that a random job applicant will be an honest worker who is cleared by the polygraph?

Transcribed Image Text:

Applicant tells truth- Applicant Lies -Polygraph says "Lie" -Polygraph says "Truth" -Polygraph says "Lie" Polygraph says "Truth"