19.4 Consider the regression model Yi = b0 + b1Xi + ui from Chapter 4, and assume that the least squares assumptions in Key Concept 4.3 hold.

a. Write the model in the matrix form given in Equations (19.2) and (19.3).

b. Show that assumptions 1 through 4 in Key Concept 19.1 are satisfied.

c. Use the general formula for B n in Equation (19.11) to derive the expressions for b n

0 and b n

1 given in Key Concept 4.2.

d. Show that the (1, 1) element of B n in Equation (19.13) is equal to the expression for s 2

b n

0 given in Key Concept 4.4.