Suppose you fit the model y = b0 + b1x1 + b2x1 2 + b3x2 + b4x1x2 to n = 20 data points with the following results: bn 0 = 5.82 bn 1 = 1.94 bn 2 = -2.11 bn 3 = 1.79 bn 4 = -.36 sbn1 = .74 sbn2 = 2.15 sbn3 = .19 sbn4 = 1.83 SSE = 1.88 R2 = .71

a. Is there sufficient evidence to conclude that at least one of the parameters b1, b2, b3, or b4 is nonzero? Test using a = .05.

b. Test H0: b1 = 0 against Ha: b1 7 0. Use a = .05.

c. Test H0: b2 = 0 against Ha: b2 6 0. Use a = .05.

d. Test H0: b3 = 0 against Ha: b3 ≠ 0. Use a = .05.