Generalizability Theory

Everyone who works in any field of science is well acquainted with the notion that whatever measure we take of whatever phenomenon, that measure is inherently affected by random error. Indeed, reliability issues are recognized as of capital importance in any scientific endeavour, as well as in psychology. Over the years, the classical test theory of measurement has been the solid ground for almost all of psychological testing. The aim of this entry is to describe generalizability theory (Brennan, 2001; Cronbach, Gleser, Nanda & Rajaratnam, 1972), which represents a more precise and complete model of the composition of an observed measure, and to show some of its advantages relative to classical test theory.

According to classical test theory, an observed score is composed of the sum ...