Abstract
It is well known that coefficient alpha can be used to estimate the reliability of a test even when the test is split into several parts. It is also known that alpha can severely underestimate test reliability when the several parts have an unequal number of items. A gernalization of alpha,β k, is proposed to correct this defect. Several properties ofβ k are also presented.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Cronbach, L. J., “Coefficient alpha and the internal structure of tests,”Psychometrika, 1951,16, 297–334.
Feldt, L. S., “Estimation of the reliability of a test divided into two parts of unequal length,”Psychometrika, 1975,40, 557–561.
Horst, P., “Estimating total test reliability from parts of unequal length,”Educational and Psychological Measurement, 1951,11, 368–371.
Kristof, W., “Estimation of reliability and true score variance from a split of a test into three arbitrary parts,”Psychometrika, 1974,39, 491–499.
Lord, F. M. and Novick, M. R.,Statistical theories of mental test scores, Reading, Mass.: Addison-Wesley, 1968.
Novick, M. R. and Lewis, C., “Coefficient alpha and the reliability of composite measurements,”Psychometrika, 1967,32, 1–13.
Rajaratnam, N., Cronbach, L. J., & Gleser, G. C., “Generalizability of Stratified—Parallel Tests,”Psychometrika, 1975,30, 39–56.
Raju, N. S., New formula for estimating total test reliability from parts of unequal length,Proceedings, 78th Annual Convention, APA, 1970, 143–144.
Rulon, P. J., “A simplified procedure for determining the reliability of a test by split-halves,”Harvard Educational Review, 1939,9, 99–103.
Author information
Authors and Affiliations
Additional information
The author gratefully acknowledges the assistance of Dr. Leonard Feldt for reviewing an earlier draft of this paper, and Ms. Rita Karwacki Bode and Mr. Dave Mansell for the analysis of the experimental data reported here. The comments of an unknown referee which contributed substantially to the clarity of the presentation are also gratefully acknowledged.
Rights and permissions
About this article
Cite this article
Raju, N.S. A generalization of coefficient alpha. Psychometrika 42, 549–565 (1977). https://doi.org/10.1007/BF02295978
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02295978