 Interaction (statistics)

A statistical interaction means that the effect of one predictor depends on another on the chosen response scale. In a linear regression, an interaction term ${\beta }_{3}XZ$ changes the slope in $X$ to ${\beta }_1+{\beta }_{3}Z$. Whether interaction is present depends on the comparison scale; additive effects and multiplicative effects use different null contrasts. Comparing subgroup effects requires an interaction contrast, rather than contrasting their separate significance labels.

In statistics, "interaction" refers to a situation in which the effect of one independent variable on a dependent variable differs depending on the level of another independent variable. In other words, the impact of one factor is not consistent across all levels of another factor; instead, the relationship is influenced or modified by the presence of the second factor. Interactions are commonly examined in the context of factorial experiments or regression models.