This paper summarizes three studies that illustrate how application of the three-parameter logistic test model helped solve three relatively intractable testing problems. The three problems are designing a multi-purpose test, evaluating a multi-level test, and equating a test on the basis of pretest statistics. Examples use information about tests in various College Board testing programs. The first two studies demonstate the value of the information function and relative efficiency. The last study is an application of basic item charcteristic curve theory and shows the potential usefulness of pre-equating. (44pp.)