Refer to the following ANOVA tables and to SAS output given here (from data in Problem 8 of Chapter 8) to answer the following questions dealing with factors related to soil erosion.
a. Using the accompanying SAS output, compute rYX2|X1 and rYX3|X1.
b. Based on your results in part (a), which variable (if any) should next be entered into a regression model that already contains X1?
c. Test H0: pYX2|X1 = 0 using the t test described in Problem 2.
d. Determine the squared multiple partial correlation r2Y(X2,X3)|X1, and test H0: pY(X2,X3)|X1 = 0.
ANOVA Table

Regression of Y on X1 and X2

Regression of Y on X1 and X3

Regression of Y on X1, X2, and X3