Refer to Exercise 12.50.

(a) Perform an analysis of covariance. Test for a difference in treatments using level of significance 0.05 .

(b) Compare your analysis in part (a) with the analysis of variance. Is the covariate important?

Data From Exercise 12.50

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12.50 The state highway department does an experiment to compare three types of surfacing treatments and the response y is road roughness. The following table also gives average daily traffic volume x. Suppose the data are, in suitable units, Treatment 2 Treatment 3 y y 423 321 321 3 957 7 9 Treatment | X 552 5 y 12 10 5 x