Rayon whiteness is an important factor for scientists dealing in fabric quality. Whiteness is affected by pulp quality and other processing variables. Some of the variables include acid bath temperature, °C (x1); cascade acid concentration, % (x2); water temperature, °C (x3); sulfide concentration, % (x4); amount of chlorine bleach, lb/min (x5); and blanket finish temperature, °C (x6). A set of data from rayon specimens is given here. The response, y, is the measure of whiteness.
Y |
x1 |
x2 |
x3 |
x4 |
x5 |
x6 |
88.7 |
43 |
0.211 |
85 |
0.243 |
0.606 |
48 |
89.3 |
42 |
0.604 |
89 |
0.237 |
0.600 |
55 |
75.5 |
47 |
0.450 |
87 |
0.198 |
0.527 |
61 |
92.1 |
46 |
0.641 |
90 |
0.194 |
0.500 |
65 |
83.4 |
52 |
0.370 |
93 |
0.198 |
0.485 |
54 |
44.8 |
50 |
0.526 |
85 |
0.221 |
0.533 |
60 |
50.9 |
43 |
0.486 |
83 |
0.203 |
0.510 |
57 |
78.0 |
49 |
0.504 |
93 |
0.279 |
0.489 |
49 |
86.8 |
51 |
0.609 |
90 |
0.220 |
0.462 |
64 |
47.3 |
51 |
0.702 |
86 |
0.198 |
0.478 |
63 |
53.7 |
48 |
0.397 |
92 |
0.231 |
0.411 |
61 |
92.0 |
46 |
0.488 |
88 |
0.211 |
0.387 |
88 |
87.9 |
43 |
0.525 |
85 |
0.199 |
0.437 |
63 |
90.3 |
45 |
0.486 |
84 |
0.189 |
0.499 |
58 |
94.2 |
53 |
0.527 |
87 |
0.245 |
0.530 |
65 |
89.5 |
47 |
0.601 |
95 |
0.208 |
0.500 |
67 |
(a) Use the criteria MSE, Cp, and PRESS to find the “best” model from among all subset models.
(b) Plot standardized residuals against Y and do a normal probability plot of residuals for the “best” model. Comment.