Assume the two samples are independant simple random samples seleceted from normally distributed populations. do not assume the populations standard deviations are equal.
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. Consturct 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