Uses and abuses of coefficient alpha
Journal/Book: Psychol Assessment. 1996; 8: 750 First St NE, Washington, DC 20002-4242. Amer Psychological Assoc. 350-353.
Abstract: The article addresses some concerns about how coefficient alpha is reported and used. It also shows that alpha is not a measure of homogeneity or unidimensionality. This fact and the finding that test length is related to reliability may cause significant misinterpretations of measures when alpha is used as evidence that a measure is unidimensional. For multidimensional measures, use of alpha as the basis for corrections for attenuation causes overestimates of true correlation. Satisfactory levels of alpha depend on test use and interpretation. Even relatively low (e.g., .50) levels of criterion reliability do not seriously attenuate validity coefficients. When reporting intercorrelations among measures that should be discriminable, it is important to present observed correlations, appropriate measures of reliability, and correlations corrected for unreliability.
Note: Article Schmitt N, Michigan State Univ, Dept Psychol, E Lansing,MI 48824 USA