This paper provides the basis for understanding score equating through item response theory (IRT). Theoretical justifications and practical advantages of IRT true-score test procedures are discussed. Three steps in the equating process are specified, and a self-test is included. (SLD)

The author describes the evolution of the Scholastic Aptitude Test (SAT). He describes some of the contributions to educational research made by inquiries based on the SAT and gives particular attention to the way scaling and equating procedures for the SAT have evolved over the last half century. (Author/JAZ)