A polynomial term–a quadratic (squared) or cubic (cubed) term turns a linear regression model into a curve. But because it is X that is squared or cubed, not the Beta coefficient, it still qualifies as a linear model. This makes it a nice, straightforward way to model curves without having to model complicated non-linear models.
But how do you know if you need one–when a linear model isn’t the best model? [Read more…] about Regression Models:How do you know you need a polynomial?