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.