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 below:

(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.

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Actual Run Factor Levels Run Molecular Number Order А В с D Weight Viscosity Low (-) High (+) 1 18 2400 1400 A (°C) 100 120 2 9. 2410 1500 B (%) 4 8 C (min) 20 D (psi) 60 3 13 2315 1520 30 4 2510 1630 75 5 3 2615 1380 11 2625 1525 7 14 2400 1500 8 17 2750 1620 2400 1400 10 7 2390 1525 11 2 2300 1500 12 10 2520 1500 13 4 2625 1420 14 19 2630 1490 15 15 2500 1500 16 20 + 2710 1600 17 1 2515 1500 18 2500 1460 19 16 2400 1525 20 12 0 0 2475 1500 + + + + + + + O + + + + + + + + 1