Interaction term
= Interaction term
An interaction term lets the effect of one predictor depend on another. In
$$
\mathbb E[Y\mid X,Z]
=\beta_0+\beta_1X+\beta_2Z+\beta_3XZ,
$$
the slope with respect to $X$ is $\beta_1+\beta_3Z$.
= Interaction term
An interaction term lets the effect of one predictor depend on another. In
$$
\mathbb E[Y\mid X,Z]
=\beta_0+\beta_1X+\beta_2Z+\beta_3XZ,
$$
the slope with respect to $X$ is $\beta_1+\beta_3Z$.