An experiment was conducted on a chemical process that produces a polymer. The four factors studied were temperature

(A), catalyst concentration (B), time (C), and pressure

(D). Two responses, molecular weight and viscosity, were observed. The design matrix and response data are shown in Table P6.8.

(a) Consider only the molecular weight response. Plot the effect estimates on a normal probability scale. What effects appear important?

(b) Use an analysis of variance to confirm the results from part (a). Is there indication of curvature?

(c) Write down a regression model to predict molecular weight as a function of the important variables.

(d) Analyze the residuals and comment on model adequacy.

(e) Repeat parts (a)–

(d) using the viscosity response.