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 17.8, 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 there a difference between the mean salary of black belts and green belts?

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Sample Size Standard Deviation Job Title 219 34 Iean 87,342 65,679 20,955 18,137 Black Belt Green belt