Researchers studied the effects of adding an exercise program to dieting in the achievement of weight loss. A sample of 15 men ages 18-20 (Group 1) were observed for weight loss using a diet only, and another independent sample of 12 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 6.7 pounds with a standard deviation of 4.2 pounds, and the mean weight loss for Group 2 was 14.1 pounds, with a standard deviation of 5.8 pounds. Calculate sp, the pooled estimate of the standard deviation, to one decimal place.