Nonlinear Models

In Chapters 9 and 10, we discussed the use of various regression models when fitting data on relationships. All models discussed in those chapters are in the class of models called “linear models,” because the parameters in the models occur in a simple linear form. That is, in the three examples from Chapters 9 and 10 shown below, the yield, y, is a linear combination of the parameters a, b, c, and d:

y = a + bx,

y = a + bx + cx

, and

y = a + bx + cz + dxz.