An engineer suspects that the surface finish of a metal part is influenced by the feed rate and the depth of cut. He selects three feed rates and four depths of cut. He then conducts a factorial experiment and obtains the following data:

Depth of Cut (in)

Feed Rate

(in/min) 0.15 0.18 0.20 0.25 74 79 82 99 0.20 64 68 88 104 60 73 92 96 92 98 99 104 0.25 86 104 108 110 88 88 95 99 99 104 108 114 0.30 98 99 110 111 102 95 99 107

(a) Analyze the data and draw conclusions. Use ???? = 0.05.

(b) Prepare appropriate residual plots and comment on the model’s adequacy.

(c) Obtain point estimates of the mean surface finish at each feed rate.

(d) Find the P-values for the tests in part (a).