(a) Choose factor settings over −1 ≤ xB, xC, xD, xE, xQ ≤ 1 to minimize MSE ̂ = (ŷ − 8) 2 + 𝜎 2 based on models (5.8) and (5.9). (b) For the setting chosen in (a), compute its ŷ, ̂𝜎2, and MSE...

(a) Choose factor settings over −1 ≤ xB, xC, xD, xE, xQ ≤ 1 to minimize

MSE ̂ = (ŷ − 8)

2 + 𝜎 2 based on models (5.8) and (5.9).

(b) For the setting chosen in (a), compute its ŷ, ̂𝜎2, and MSE values. Compare ̂ them with those obtained in Section 5.3 and in Exercise 1. If you want to

further reduce these values, do you need to relax the range of the factor

levels? Which factor would you consider first?

(c) Repeat the work in (a) by relaxing the range of one factor you chose in

(b). Comment on the improvement and the need for extrapolation.