A formula for calculating stratified alpha (α.) is presented using analysis-of-variance notation. When test items are randomly selected from strata that differ in content or difficulty, α, is more appropriate than alpha (α) as a measure of internal consistency.
References
1.
CronbachL. J.Coefficient alpha and the internal structure of tests. Psychometrika, 1951, 16, 297–334.
2.
CronbachL. J.SchoenemannP.McKieD.Alpha coefficients for stratified-parallel tests. Educational and Psychological Measurement, 1965, 25, 291–312.
3.
RajaratnamN.CronbachL. J.GleserG. C.Generalizability of stratified-parallel tests. Psychometrika, 1965, 30, 39–56.
