Referring to Problem 15-75, suppose the manager of McCracken’s marketing department questions the appropriateness of adding a second variable. How would you respond to her question?
In exercise
Describe the regression model at Step 2 of the analysis. In your discussion, be sure to discuss the effect of adding a new variable on the standard error of the estimate and on R2.
The J. J. McCracken Company has authorized its marketing research department to make a study of customers who have been issued a McCracken charge card. The marketing research department hopes to identify the significant variables that explain the variation in purchases. Once these variables are determined, the department intends to try to attract new customers who would be predicted to make a high volume of purchases.
Twenty-five customers were selected at random, and values for the following variables were recorded in the file called McCracken:
y = Average monthly purchases 1 in dollars 2 at McCracken
x1 = Customer age
x2 = Customer family income
x3 = Family size