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. For the survey, emails were sent to 57,029 members, and 7,036 valid responses were received. The two most common job titles were manager and quality engineer. Another title is Master Black Belt, a person who takes a leadership role as the keeper of the Six Sigma process (see Section 18.6). An additional title is Green Belt, someone who works on Six Sigma projects part time. Descriptive statistics concerning salaries for these four titles are given in the following table:

Compare the salaries of Green Belts, managers, quality engineers, and Master Black Belts.