Problem 1.61 The data in Problem 1.18 come from an experiment where the goal is to control all the factors except the one we are testing. The factors of age and neighborhood were controlled by pairing the children of the same age and neighborhood; they differed with respect to their parents’ exposure to lead. This is an example of paired data. One way of comparing the blood lead levels between the two populations is to compute the sample mean and sample standard deviation of D, the difference between the exposed and control group of children. Calculate the sample mean and sample standard deviation for the variable D and interpret your results.