What Are Quadratic Models?

A quadratic function is written like this:

Theory

Quadratic Model

f(x) = ax2 + bx + c

Here are a couple of examples of the graphs of quadratic functions:


Graphs of quadratic model

Figure 1: a > 0 the graph is convex, a < 0 the graph is concave

You use the quadratic model when your points lie in a convex or concave arc. But you can also use other polynomial functions in those cases. You can test different polynomial functions to see what gives the best fit.

A typical situation where using a quadratic model for your data points makes sense is when you assume that what you’re modeling has a maximum or minimum. For example, if you want to model a javelin throw, you know that the height of a javelin throw has a maximum. That means a quadratic model would fit the data well.

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