Lyle et al. (1987) ran an experiment to study the effect of a calcium supplement on the blood pressure of African American males. A group of 10 men received a calcium supplement, and another group of 11 men received a placebo. The experiment lasted 12 weeks. Both before and after the 12-week period, each man had his systolic blood pressure measured while at rest. The changes (after minus before) are given in Table 9.2. Test the null hypothesis that the mean change in blood pressure for the calcium supplement group is lower than the mean change in blood pressure for the placebo group. Use level α0 = 0.1.