Long-term exposure to stress can result in a variety of health problems. A study tested the effects of cortisone, the primary stress hormone, on the memory retention of 12 individuals. Subjects were shown a set of 60 words and 24 hours later were asked to recall as many words as they could remember. One hour before the retention test, subjects received a dose of either cortisone or a placebo. Then, two weeks later the same procedures were repeated with the same individuals, but with a different set of 60 words and with subjects receiving the opposite treatment than they received the first week. The number of words retained for both treatments is listed below. Does cortisone decrease longterm memory? You may assume that the sample was drawn from a normal distribution. Take a = 0.05. Individual Number Placebo Cortisone 14 11 16 12 11 10 12 9 15 13 15 12 17 14 14 9 15 11 12 9 16 10 13 14