Since lower complexity models are easier to implement, it becomes necessary to remove the restriction that data points are met exactly by only requiring that the model be "close" to the data points using some measure of closeness. This chapter provides a scheme using calculus extrema for creating an approximate model that "best" approximates any number of data points but with a relatively low complexity model. You will use the resulting model in this chapter as a descriptive measure for the data. Other courses may use similar techniquest to make inferences but that is for one of those courses.