Intraclass Correlation as an Approximation to the Coefficient of Generalizability

Abstract

The theory of generalizability (Cronbach, et al., 1963) regards a measure as sampled from a universe of comparable but not necessarily equivalent measures. The most suitable index of agreement would be the average of the squared correlations of the measures with the average of all measures. Since this cannot be directly determined, the intraclass coefficient is used. Comparison of the two indices for hypothetical universes shows that they agree closely, save for types of universe unlikely to be found in practice.