Effect of Marijuana Use on College Students Many studies have been conducted to test the effects of marijuana use on mental abilities. In one such study, groups of light and heavy users of marijuana in college were tested for memory recall, with the results given below (based on data from “The Residual Cognitive Effects of Heavy Marijuana Use in College Students,” by Pope and Yurgelun-Todd, Journal of the American Medical Association, Vol. 275, No. 7).

a. Use a 0.01 significance level to test the claim that the population of heavy marijuana users has a lower mean than the light users. Should marijuana use be of concern to college students?

b. Construct a 98% confidence interval for the difference between the two population means.

Does the confidence interval include zero? What does the confidence interval suggest about the equality of the two population means?

Items sorted correctly by light marijuana users: n = 64, x = 53.3, s = 3.6 Items sorted correctly by heavy marijuana users: n = 65, x = 51.3, s = 4.5