12.11 Consider the following estimated linear regression equations:

Y = a0 + a1X1 Y = b0 + b1X1 + b2X2

a. Show in detail the coefficient estimators for a1 and b1 when the correlation between X1 and X2 is equal to 0.

b. Show in detail the coefficient estimators for a1 and b1 when the correlation between X1 and X2 is equal to 1.

The following exercises require the use of a computer.