What type of regression line is indicated by a cubic equation?

A cubic equation indicates a relationship where the dependent variable is modeled as a cubic polynomial of the independent variable. This means that the equation includes terms where the variable is raised to the third power, which leads to a mathematical representation that forms a curve rather than a straight line.

In a cubic regression, as you change the values of the independent variable, the output can change in a non-linear fashion, resulting in a curve. The characteristics of the cubic function allow it to have one or multiple turning points, which contributes to its curved shape. This is distinctly different from constant, straight, or exponential lines, which have their own specific relationships with respect to their variables.

Thus, recognizing that a cubic equation inherently describes a non-linear relationship helps in understanding why the correct choice is described as a curved line.