Thepercentage of hardwood concentration in raw pulp, the vat pressure, and the cooking time of the pulp are being investigated for their effects on the strength ofpaper. Three levels of hardwood concentration, three levels of pressure, and two cooking times are selected. A factorialexperiment with two replicates is conducted, and the following data are obtained: Percentage Cooking time 3.0 hours Cooking time 4.0 hours
of Hardwood Pressure Pressure
Concentration 400 500 650 400 500 650
2 196.6 197.7 199.8 198.4 199.6 200.6
196.0 196.0 199.4 198.6 200.4 200.9
4 198.5 196.0 198.4 197.5 198.7 199.6
197.2 196.9 197.6 198.1 198.0 199.0
8 197.5 195.6 197.4 197.6 197.0 198.5
196.6 196.2 198.1 198.4 197.8 199.8
(a) Analyze the data and draw conclusions. Use α =0.05.
(b) Prepare appropriate residual plots and comment on the model’ sadequacy.
(c) Under what set of conditions would you run the process? Why?