When linear models include more than one explanatory variable, there will always be an interaction between them.

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Quizplus · Accepted Answer

Including more than one explanatory variable in a linear model does not automatically imply there will be an interaction between them. Interaction effects are specific terms added to a model to capture the effect of one variable on the response variable changes across the levels of another variable. Without explicitly including interaction terms, the model assumes the effects of the explanatory variables are additive and independent.

When Linear Models Include More Than One Explanatory Variable, There