Published Online: 30 JAN 2010
Copyright © 2010 John Wiley & Sons, Inc. All rights reserved.
Corsini Encyclopedia of Psychology
How to Cite
Steedle, J. T. and Shavelson, R. J. 2010. Coefficient Alpha. Corsini Encyclopedia of Psychology. 1.
- Published Online: 30 JAN 2010
Because test scores are known to contain errors, test developers and administrators must concern themselves with test score consistency (or reliability). Such concerns are commonly investigated using coefficient alpha, an internal consistency reliability coefficient that is computed as follows:
where k is the number of test items, is the variance of scores on item i, and is the variance of total test scores. Alpha is generally applicable for studying reliability on a single test at one point in time from multiple observations on individuals (e.g., scores on test items, task-performance ratings from multiple judges).
- classical test theory;
- generalizability theory;