11.75 Refer to Exercise 11.74. Suppose the proposed second-order model is fit to a total of 50 observations on delivery time. The sum x2 = distance to be shipped x1 = b 1 if rail 0 if truck Y = shipping time E(Y ) = b0 + b1x1 + b2x2 + b3x1x2 + b4x2 2 bN 2

b2 a = 0.01 sb N 1 = 0.231 sb N 2 = 0.48 yN = 0.11 + 0.98x1 - 0.53x2 n = 42 x2 = b 1 if plant A (dummy variable)

0 if plant B of squared errors is . Then the reduced model is fit to the same data, and SSE = 259.34.Test to see whether the data indicate that the mean delivery time differs for rail and truck deliveries.