Two units make up this material. They focus on applications of second-order difference equations to American politics. The goals of the first module include helping the user understand: 1) the difference between a theoretical construct and an observable; 2) the nature of choices which exist in modeling any particular empirical phenomenon; and 3) more about difference equations. The second module encompasses the goals listed above, as it is a continuation of an analysis of Supreme Court decision-making. Exercises are included, with answers, in each of the units. (MP)