Suppose That the Sample Regression Equation of a Model Is $= 10 + 4 x _ { 1 } + 3 x _ { 2 } - x _ { 1 } x _ { 2 }$

Multiple Choice

Suppose that the sample regression equation of a model is $= 10 + 4 x _ { 1 } + 3 x _ { 2 } - x _ { 1 } x _ { 2 }$ . If we examine the relationship between $x _ { 1 }$ and y for three different values of $x _ { 2 }$ , we observe that the:

A) three equations produced differ only in the intercept.
B) coefficient of $x _ { 2 }$ remains unchanged.
C) coefficient of $x _ { 1 }$ varies.
D) three equations produced differ not only in the intercept term but the coefficient of $x _ { 1 }$ , also varies.