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Suppose a college career center was interested in the starting salaries of recent graduates in Communications Studies and Sociology. The center randomly samples 15 recent graduates from each of these fields and records the starting salary for the graduates. The center wants to determine whether there is a difference in the starting salaries for graduates in these majors. Which test(s) should be used in each of these situations? a. Assume the starting salary for both majors is approximately Normally distributed. b. Assume that one of the salary distributions is strongly right-skewed.

Short Answer

Expert verified
a. Independent two-sample t-test. b. Mann-Whitney U test.

Step by step solution

01

Situation A: Normally Distributed Salaries

When the starting salaries for both majors are approximately Normally distributed, the appropriate test to use is the independent two-sample t-test. The t-test is robust to the assumption of normality and compares the means of two groups. To perform the t-test, list the starting salary data for both majors, calculate the mean and variance for each group, then use these values in the t-test formula.
02

Situation B: One Salary Distribution is Strongly Right-Skewed

If one of the salary distributions is strongly right-skewed, i.e., it has a tail on the right side, indicating a few very high values, then the distribution deviates from normality. In this case, the appropriate test to use is the non-parametric Mann-Whitney U test (also known as the Wilcoxon rank-sum test). This test does not require the assumption of normal distribution and can handle skewed data. To perform this test, you will rank all the data from both groups together, then add up the ranks for each group and use these sums in the Mann-Whitney U test formula.

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