Ledolter and Hogg (see References) report the comparison of three workers with different experience who manufacture brake wheels for a magnetic brake. Worker A has four years of experience, worker B has seven years, and worker C has one year. The company is concerned about the product€™s quality, which is measured by the difference between the specified diameter and the actual diameter of the brake wheel. On a given day, the supervisor selects nine brake wheels at random from the output of each worker. The following data give the differences between the specified and actual diameters in hundredths of an inch:

(a) Test whether there are statistically significant differences in the quality among the three different workers.
(b) Do box plots of the data confirm your answer in part (a)?

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Worker A: 2.0 3.0 2.3 3.5 3.0 2.0 4.0 4.5 3.0 Worker B: 1.5 3.0 4.5 3.0 3.0 2.0 2.5 1.0 2.0 Worker C: 2.5 3.0 2.0 2.5 1.5 2.5 2.5 3.0 3.5