This book is combined with a Web site to allow the reader to acquire the basic concepts of item response theory without becoming enmeshed in the underlying mathematical and computational complexities. The first edition, with its accompanying software, was designed to give the reader access to the basic concepts of item response theory without having to do the tedious mathematics. This edition contains an annotated list of recommended readings and Web resources and updated software for the Internet. The book is organized in a building block fashion, proceeding from the simple to the complex, with each new topic building on the previous topics. Within each chapter, a basic concept is presented, the corresponding computer sessions are explained, and a set of exploratory exercises is defined. The chapters are: (1) "The Item Characteristic Curve"; (2) "Item Characteristic Curve Models"; (3) "Estimating Item Parameters"; (4) The Test Characteristic Curve"; (5) "Estimating an Examinee's Ability"; (6) "The Information Function"; (7) "Test Calibration"; and (8) "Specifying the Characteristics of a Test." (Contains 10 tables, and 21 figures.) (SLD)