30. The objectives of a study by Steinhardt et al. (A-32) were (1) to determine if level of physical activity and cardiovascular fitness were significantly related to absenteeism and medical care claims among law enforcement officers over a one-year period and (2) to determine if moderate levels of physical activity and fitness were inversely associated with reduced absenteeism and medical care claims. Subjects for the study were law enforcement officers in the city of Austin, Texas. Among other findings, the investigators reported that 65 subjects whose physical activity level was categorized as sedentary were absent, on the average, 10.04 days per year with a standard deviation of 9.65. The mean and standard deviation for 275 subjects who were physically active three times per week were 6.04 and 6.59, respectively. Construct a 95 percent confidence interval for the difference in population means. State the assumptions that make your procedure valid.

What do you conclude from your findings?