A polygraph (lie detector) is an instrument used to determine if the individual
ID: 3182083 • Letter: A
Question
A polygraph (lie detector) is an instrument used to determine if the individual is telling the truth. These tests are considered to be 92% reliable. In other words, if an individual lies, there is a 0.92 probability that the test will detect a lie. Let there also be a 0.004 probability that the test erroneously detects a lie even when the individual is actually telling the truth. Consider the null hypothesis, "the individual is telling the truth," to answer the following questions. a. What is the probability of Type I error? (Round your answer to 3 decimal places.) Probability b. What is the probability of Type II error? (Round your answer to 2 decimal places.) Probability
Explanation / Answer
a) P (Type I error) = P(Rejecting True null)
= P(erroneous detection of lie even when it is the truth)
= 0.004
b) P (Type II error) = P(Failing to reject false Null)
= P(Not detecting a lie)
= 1-0.92
= 0.08