Scatterplots and other such graphs can help you visualize relationships between variables. Once you have visualized relationships, the next step is to analyze those relationships so that you can describe them numerically. That numerical description of the relationship between variables is called a model. Even more importantly, a model also predicts the average value of one variable (Y) from the value of another variable (X). The X variable is also called a predictor. Generally, this model is called a regression model.
Note: Only the basic platforms and options are covered here. For complete details and explanations of all platform options, see Basic Analysis, Essential Graphing, and the books listed in About This Chapter.
Table .3 shows the four primary types of relationships.