Use the coal cleansing data of Exercise 15.2 on page 609 to fit a model of the type E(Y ) = 0 + 1x1 +

Use the coal cleansing data of Exercise 15.2 on page 609 to fit a model of the type E(Y ) = β0 + β1x1 + β2x2 + β3x3, where the levels are x1, percent solids: 8, 12 x2, flow rate: 150, 250 gal/min x3, pH: 5, 6 Center and scale the variables to design units. Also conduct a test for lack of fit, and comment concerning the adequacy of the linear regression model.