Education Journal


1995.第23卷第1期(Vol. 23 No. 1).pp. 135–146



Reliability and Dimensionality — Scales with High Alpha Coefficients Are not Necessarily Unidimensional

侯傑泰(Kit-Tai HAU)




In psychological, educational, and social research involving self-constructed or standardized tests, the reliability and validity of the instruments are of great concern to the researchers. Customarily, reliability (particularly Cronbach's alpha), internal consistency, homogeneity, and unidimensionality are used, sometimes interchangeably and quite confusingly, to describe the relationships among the items in the same scale. However, there is a common misconception that alpha value and dimensionality have a one-one correspondence relation. The present article reviews the problems associated with using alpha as an indicator of unidimensionality. Furthermore, using simulated data, it is demonstrated that high alpha does not guarantee unidimensionality and low alpha does not imply multidimensionality.