=+Obs Formaldehyde concentration Catalyst ratio Curing temperature Curing time Durable press rating 6 7 7 180 1 4.7 7 7 13 140 1 4.6 8 5 4 160 7 4.5 9 4 7 140 3 4.8 10 5 1 100 7 1.4 11 8 10 140 3 4.7 12 2 4 100 3 1.6 13 4 10 180 3 4.5 14 6 7 120 7 4.7 15 10 13 180 3 4.8 16 4 10 160 5 4.6 17 4 13 100 7 4.3 18 10 10 120 7 4.9 19 5 4 100 1 1.7 20 8 13 140 1 4.6 21 10 1 180 1 2.6 22 2 13 140 1 3.1 23 6 13 180 7 4.7 24 7 1 120 7 2.5 25 5 13 140 1 4.5 26 8 1 160 7 2.1 27 4 1 180 7 1.8 28 6 1 160 1 1.5 29 4 1 100 1 1.3 30 7 10 100 7 4.6

d. Now consider models based not only on these four independent variables but also on secondorder predictors (four xi 2