The design factors are A, B, C, and D, each at three levels. These are assigned to an orthogonal array (inner array) with the factors A, B, C, and D assigned to columns 1, 2, 3, and 4, respectively. Suppose that in addition to the three main effects of the noise factors E, F, and G, it is felt that the interaction effects E x F and E x G should be investigated. What type of design would you use for the outer array?
Suppose the outer array selected is L8, with the assignments as follows: E to column 1, F to column 2, E x F to column 3, G to column 4, and E x G to column 5. The remaining two columns are assigned to the experimental error. Table 12-46 shows the moisture content of the eight replications for each of the nine experiments in the inner array. The coded target value is 20.
Show the complete parameter design layout using the Taguchi method. Calculate the mean response and the appropriate signal-to-noise ratios. Plot the average S/N ratios and the average responses, and discuss how the design factor levels are to be selected. Use the average response plots to determine the existence of the interaction effects A x E, B x F, E x F, and E x G. What are the optimal settings of the design parameters using Taguchi's parameter design approach?

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