Suppose a professional job-placement firm that monitors salaries in professional fields is interested in determining if the fluctuating price of oil and the outsourcing of computer-related jobs have had an effect on the starting salaries of chemical and electrical engineering graduates. Specifically, the job-placement firm would like to know if the 2007 average starting salary for chemical engineering majors is higher than the 2007 average starting salary for electrical engineering majors. To conduct its test, the job-placement firm has selected a random sample of 124 electrical engineering majors and 110 chemical engineering majors who graduated and received jobs in 2007. Each graduate was asked to report his or her starting salary. The results of the survey are contained in the file Starting Salaries.
a. Conduct a hypothesis test to determine whether the mean starting salary for 2007 graduates in chemical engineering is higher than the mean starting salary for 2007 graduates in electrical engineering. Conduct the test at the 0.05 level of significance. Be sure to state a conclusion. (Assume that the firm believes the two populations from which the samples were taken are approximately normally distributed with equal variances.)
b. Suppose the job-placement firm is unwilling to assume that the two populations are normally distributed with equal variances. Conduct the appropriate hypothesis test to determine whether a difference exists between the mean starting salaries for the two groups. Use a level of significance of 0.05. What conclusion should the job-placement firm reach based on the hypothesis test?