Many studies have been conducted to the 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. 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?
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
Construct a 98% confidence interval for the difference between the population means. Does the confidence interval include zero? What does the confidence interval suggest about the quality of the two population means?