Calculating VIFs typically involves running sets of auxiliary regressions, one regression for each independent variable in an equation. To get practice with this procedure, calculate the following:

a. The VIFs for N, P, and I from the Woody’s data in Table 3.1

b. The VIFs for BETA, EARN, and DIV from the stock price example data in Table 7.2

c. The VIF for X₁ in an equation where X₁ and X₂ are the only independent variables, given that the VIF for X₂ is 3.8 and N = 28

d. The VIF for X₁ in an equation where X₁ and X₂ are the only independent variables, given that the simple correlation coefficient between X₁ and X₂ is 0.80 and N = 15