ABSTRACT
There is more than one way to make a model. One approach, and the one taken in most of the chapters of this book, is to start with some idea, or theory, about the way the real world works. From this theory, we next create a model from which we can make predictions. Finally, we compare the predictions of the model with the behaviour of the real world. If there is close agreement, we say that it is a good model; if not, we start again.
