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 14.6 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?

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Job Tithe Black belt Green belt Sample Stze Mean 93,123 73,045 Standard Deviation 21.186 21.272 128 39