A two-level factorial experiment in four factors was conducted by Chrysler and described in the article Sheet

A two-level factorial experiment in four factors was conducted by Chrysler and described in the article €œSheet Molded Compound Process Improvement€ by P. I. Hsieh and D. E. Goodwin (Fourth Symposium on Taguchi Methods, American Supplier Institute, Dearborn, MI, 1986, pp. 13€“21). The purpose was to reduce the number of defects in the finish of sheet-molded grill opening panels. A portion of the experimental design, and the resulting number of defects, yi observed on each run is shown in the following table. This is a single replicate of the 24 design. 

(a) Estimate the factor effects and use a normal probability plot to tentatively identify the important factors.

(b) Fit an appropriate model using the factors identified in part (a).

(c) Plot the residuals from this model versus the predicted number of defects. Also prepare a normal probability plot of the residuals. Comment on the adequacy of these plots.

(d) The following table also shows the square root of the number of defects. 

Repeat parts (a) and (c) of the analysis using the square root of the number of defects as the response. Does this change the conclusions?

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Grill Defects Experiment в с D у Run 1 56 7.48 2 17 4.12 3. 2 1.41 4 4 2.00 5 3 1.73 6. 4. 2.00 50 7.07 1.41 9. 1 1.00 10 0.00 11 3 1.73 12 12 3.46 13 1.73 14 4 2.00 15 0.00 16 0.00 |II I III| + + + |||| + + + I +I + I +I + | +| +I + I +