2. An experiment was conducted to compare the mean absorption of two drugs in muscle tissue. Muscle tissue specimens were randomly divided into two groups of equal size. Group 1 was tested with Drug 1 and Group 2 was tested with Drug 2. Assuming that the absorption rate is approximately normally distributed for each drug with equal population standard deviation, a 99% confidence estimate for the difference in population means (Group 1 mean minus Group 2 mean) is (-0.1067, 0.5407).

(a) Explain why the sample standard deviations should be pooled in this situation.

(b) Explain why this confidence interval does not provide statistical evidence that there is a difference in mean absorption.