ABSTRACT
The last chapter was concerned solely with a relationship, assumed to be linear, between two variables where one, y, was assumed to be dependent on the other, x. In real-world situations, we are likely to be concerned with more complex relationships estimated in different environments and with examining the possible dependence of y on several x variables. First, however, we will consider the situation where the relationship between y and x is not linear, that is, cannot be represented by a straight line.
