Once Interaction Has Been Established Between $x _ { 1 }$

True/False

Once interaction has been established between $x _ { 1 }$ and $x _ { 2 }$ , the first-order terms for $x _ { 1 }$ and $x _ { 2 }$ may be deleted from the regression model leaving the higher-order term containing the product of $x 1$ and $x _ { 2 }$ .