DuPont conducted a field experiment for an improved version of Teflon several years after they first introduced Teflon. Four cities received 10 day-time commercial minutes per week during the fall months, five cities received 5 minutes per week, and four cities (the control group) received no advertising. Cities were randomly assigned to each of the three test conditions. The sales measure was a purchase of Teflon cookware as reported by telephone interviews with 1,000 housewives in each of the test cities. The total purchases turned out to be about 30 percent higher in the heavy-advertising cities than in those cities with no or low advertising, but there was no real difference between the low and no-advertising groups. Critique this test. What validity problems do you see? What changes would you make? Would you conduct the same test if the product change had been out for three years?