² See Shea Gibbs and Rajkumar Venkatesan, “Multiple Regression in Marketing-Mix Models,” UVA-M-0855 (Charlottesville, VA: Darden Business Publishing, 2013) for a discussion of linear regressions; see Shea Gibbs and Rajkumar Venkatesan, “Logistic Regression,” UVA-M-0859 (Charlottesville, VA: Darden Business Publishing, 2013) for more on logistic regression analyses.