EXAMPLE 7 Validating Truthfulness and Encouraging Honesty

In a major national study, researchers were concerned about the truthfulness of student answers to questions about illicit drug use. Researchers compared data among twelfth-graders’ responses to questions about their own drug use, their friends’ drug use, and their own exposure to drug use. in any given year, comparisons across these three measures tended to be consistent from drug to drug. Because respondents should have little reason to answer untruthfully about their friends or their general exposure to drugs, the researchers considered this consistency as evidence of the truthfulness of student responses about their own drug use.

Another strategy for encouraging honesty with sensitive topics is called randomized response, invented by sociologist S. L. Warner in 1965 and explored in Exercises 20 and 21 (page 331). By introducing randomness into the responses in a structured way, researchers use their knowledge of probability distributions to get reasonably accurate information about the overall group while allowing each potentially embarrassing answer to be “camouflaged.” Because the interviewee knows that, for example, the researcher has no way to distinguish which “yes” answers are real and which are simply introduced by the random mechanism, they will feel safe answering honestly a question of the form “Have you ever done [some embarrassing or illegal action]?”