paired or not? part i. in each of the following scenarios, determine if the data are paired. (a) compare pre- (beginning of semester) and post-test (end of semester) scores of students. (b) assess gender-related salary gap by comparing salaries of randomly sampled men and women. (c) compare artery thicknesses at the beginning of a study and after 2 years of taking vitamin e for the same group of patients. (d) assess effectiveness of a diet regimen by comparing the before and after weights of subjects.