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# Example 135

Example 135: The World Anti-Doping Agency funded a study to compare the effects of Growth Hormone on body composition and athletic performance in women. Among the 16 subjects assigned to the placebo group, the mean fat mass change after eight weeks was -2.1 pounds with a standard deviation of 1.2 pounds. Among the 17 subjects assigned to injections of growth hormone, the mean fat mass change after eight weeks -4.4 pounds with a standard deviation of 1.3 pounds. Construct a 95% confidence interval estimate of the difference between the mean weight losses for the two diets (assume weight loss is a normally distributed random variable and assume the two groups have equal variances). Does it seem that growth hormone has an effect on fat mass in women?