The history of generalizability theory (G theory) is told from the perspective of one researcher's experiences, describing psychometric and scientific perspectives that influenced the development of G theory and its adoption. Work that remains to be done in the field is outlined. (SLD)

The framework and procedures of generalizability theory are introduced and illustrated in this instructional module that uses a hypothetical scenario involving writing proficiency. Generalizability analyses are useful for understanding the relative importance of various sources of error and for designing efficient measurement procedures. (SLD)