Suppose we have a data set with five predictors, X₁ = GPA, X₂ = IQ,
X₃ = Gender (1 for Female and 0 for Male), X₄ = Interaction between
GPA and IQ, and X5 = Interaction between GPA and Gender. The
response is starting salary after graduation (in thousands of dollars).
Suppose we use least squares to fit the model, and get β₀ = 50, β₁ =
20, β₂ = 0.07, β₃ = 35, β₄ = 0.01, β₅ = −10.