Suppose you fit the model y = b0 + b1 x1 + b2 x21

+ b3 x2 + b4 x1 x2 + e to n = 25 data points and find that b n 0 = 1.24 b n 1 = -2.43 b n 2 = .03 b n 3 = .65 b n 4 = 1.75 sbn 1

= 1.15, sbn 2

= .18, sbn 3

= .30, sbn 4

= 1.49 SSE = .47, R2

= .85

a. Is there sufficient evidence to conclude that at least one of the parameters b1, b2, b3, and b4 is nonzero?

Test, using a = .05.

b. Test H0: b1 = 0 against Ha: b1 6 0. Use a = .05.

c. Test H0: b2 = 0 against Ha: b2 7 0. Use a = .05.

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