14.34 ● This exercise requires the use of a computer package.

The accompanying data resulted from a study of the relationship between y 5 brightness of finished paper and the independent variables x1 5 hydrogen peroxide

(% by weight), x2 5 sodium hydroxide (% by weight), x3 5 silicate (% by weight), and x4 5 process temperature (“Advantages of CE-HDP Bleaching for High Brightness Kraft Pulp Production,” TAPPI [1964]: 107A–

173A).

x1 x2 x3 x4 y .2 .2 1.5 145 83.9 .4 .2 1.5 145 84.9 .2 .4 1.5 145 83.4 .4 .4 1.5 145 84.2 .2 .2 3.5 145 83.8 .4 .2 3.5 145 84.7 .2 .4 3.5 145 84.0 .4 .4 3.5 145 84.8 .2 .2 1.5 175 84.5 .4 .2 1.5 175 86.0 .2 .4 1.5 175 82.6 .4 .4 1.5 175 85.1 .2 .2 3.5 175 84.5 .4 .2 3.5 175 86.0 .2 .4 3.5 175 84.0 .4 .4 3.5 175 85.4 .1 .3 2.5 160 82.9 .5 .3 2.5 160 85.5 .3 .1 2.5 160 85.2 .3 .5 2.5 160 84.5 .3 .3 0.5 160 84.7 .3 .3 4.5 160 85.0 .3 .3 2.5 130 84.9 .3 .3 2.5 190 84.0 .3 .3 2.5 160 84.5 .3 .3 2.5 160 84.7 .3 .3 2.5 160 84.6 .3 .3 2.5 160 84.9 .3 .3 2.5 160 84.9 .3 .3 2.5 160 84.5 .3 .3 2.5 160 84.6

a. Find the estimated regression equation for the model that includes all independent variables, all quadratic terms, and all interaction terms.