You know the grade point averages (GPAs) of a random sample of 10 full-time college students and 10 part-time college students. You want to test the hypothesis that the typical GPAs for full-time and part-time college students are different. Which test(s) should you choose for each situation? 

a. Suppose your preliminary investigation lead you to conclude that the distributions of GPAs for both groups are approximately Normal. 

b. Suppose your preliminary investigation lead you to conclude that the distributions of GPAs for both groups are not Normal but have the same shape.

Choose from the following tests, as appropriate: paired t-test, sign test, two-sample t test, and Mann-Whitney test. There may be two acceptable choices.