The American Society for Quality (ASQ) conducted a salary survey of all its members. ASQ members work in all areas of manufacturing and service-related institutions, with a common theme of an interest in quality. Two job titles are black belt and green belt. (See Section 18.6 for a description of these titles in a Six Sigma quality improvement initiative.) Descriptive statistics concerning salaries for these two job titles are given in the following table:

a. Using a 0.05 level of significance, is there a difference in the variability of salaries between black belts and green belts?
b. Based on the result of (a), which t test defined in Section 10.1 is appropriate for comparing mean salaries?
c. Using a 0.05 level of significance, is the mean salary of black belts greater than the mean salary of green belts?