Congeneric and (essentially) tau-equivalent estimates of score reliability: what they are and how to use them.
- Resource Type
- Journal Article
- Authors
- Graham JM
- Source
- Educational & Psychological Measurement. Dec2006, Vol. 66 Issue 6, p930-944. 15p.
- Subject
- Language
- ISSN
- 0013-1644
Coefficient alpha, the most commonly used estimate of internal consistency, is often considered a lower bound estimate of reliability, though the extent of its underestimation is not typically known. Many researchers are unaware that coefficient alpha is based on the essentially tau-equivalent measurement model. It is the violation of the assumptions required by this measurement model that are often responsible for coefficient alpha's underestimation of reliability. This article presents a hierarchy of measurement models that can be used to estimate reliability and illustrates a procedure by which structural equation modeling can be used to test the fit of these models to a set of data. Test and data characteristics that can influence the extent to which the assumption of tau-equivalence is violated are discussed. Both heuristic and applied examples are used to augment the discussion. [ABSTRACT FROM AUTHOR]