The yield of a chemical process is being studied. The two most important variables are thought to be the pressure and the temperature. Three levels of each factor are selected, and a factorial experiment with two replicates is performed. The yield data follow:.

emperature 150 160 170 200 90.1 90.3 90.5 90.7 90.4 90.2 Pressure 215 90.5 90.6 90.8 90.9 90.7 90.6 230 89.9 90.1 90.4 90.1 90.2 90.4

a) Analyze the data and draw conclusions. Use α = 0.05.

b) Prepare appropriate residual plots and comment on the model’s adequacy.

c) Under what conditions would you operate this process?(a