Dr. Sheffield is a clinical psychologist who specializes in treating pathological gambling. Pathological gambling is defined as being unable to resist impulses to gamble. Bothered by not having a good measure that he can give to clients to determine whether they are suffering from this condition, he creates a new measure of pathological gambling. The measure has 15 questions, and it takes 20 minutes to complete. To test his measure, Dr. Sheffield gives his measure to a group of people in Gamblers Anonymous (GA), whose behavior has already been documented. He finds that people in the GA group have high scores on his new measure. This procedure is known as a: