Unsurelock the detective knows that one of 20 suspects has committed a crime. He proposes to administer a lie-detector test to all 20 and to arrest anyone who fails the test. Which error of thinking has he made?

Question

Quizplus · Accepted Answer

The detective has overlooked the base-rate information, which refers to the probability of a person from a particular group committing a crime. It is unlikely that all 20 suspects are involved in the crime, and the use of lie-detector tests may not be a reliable way of identifying the perpetrator. By failing to consider the base-rate information, the detective may be making an erroneous assumption that everyone has an equal chance of being guilty, which is not necessarily true.

Unsurelock the Detective Knows That One of 20 Suspects Has