Consider Exercise 11-48. 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 × F and E ×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 × F to column 3, G to column 4, and E ×G to column 5. The remaining two columns are assigned to the experimental error. Table

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TABLE 11-45 Inner-Array Experiment 1 23456789 Outer-Array Experiment 1 2 3. 4 18.5 21.2 20.5 19.3 16.8 17.3 20.9 18.5 21.1 21,8 20.6 19.4 20.2 17.7 19.8 20.8. 16.2 21.5 21.2 21.4 18.3 18.5 17.8 17.2 20.6 21.4 16.8 19.5 17.5 20.0 21.0 20.4 20.4 18.8 19.6 18.3