Which is correct and most complete?

a. People almost never make design decisions using FF experiments.

Instead, they use results to pick factors for RSM experiments.

b. Lenth’s method is designed to find significance even when interactions exist.

c. DOE matrices are completely random collections of -1s & 1s.

d. All of the above are correct.

e. All of the above are correct except

(a) and (d).