Consider the first-order model ̂y = 150 + 20x1 +

12x2. If the experimenter used one coded unit in the x1 direction as the step size, the point x1 = 1.5, x2 = 1.0 is a point on the path of steepest ascent.

(a) True

(b) False 11.43 Consider the first-order model in Problem 11.42. The design used to fit this model was a 22 factorial with three center points. The variance of the predicted response at the point x1 = 1.5, x2 = 1.0 is .