Two groups of patients were selected at random from among the population of people having elevated blood pressure. The first group of 110 patients were given blood pressure medicine A, and it was determined that they obtained a mean reduction in systolic blood pressure of 15 units with a standard deviation of 5 units. The second group of 120 patients were given blood pressure medicine B, and these patients obtained a mean reduction of systolic blood pressure of 19 units with a standard deviation of 7.25 units. Find a 95% confidence interval for the difference in mean blood pressure reduction for the two medicines. Can we conclude that one medicine is more effective than the other?