Researchers studied the effects of adding an exercise program to dieting in the achievement of weight loss. A sample of 45 men ages 18-20 (Group 1) were observed for weight loss using a diet only, and another independent sample of 52 men ages 18-20 (Group 2) were put on the same diet, but with an added exercise program. The mean weight loss for Group 1 was 7.1 pounds with a standard deviation of 4.7 pounds, and the mean weight loss for Group 2 was 14.7 pounds, with a standard deviation of 4.9 pounds.
Calculate the lower bound of a 90% confidence interval for the difference in mean weight loss for the two groups.