Journal Article

Part II: On the Use, the Misuse, and the Very Limited Usefulness of Cronbach’s Alpha: Discussing Lower Bounds and Correlated Errors

Pfadt, Julius M., Sijtsma, Klaas

2021

Overview

Prior to discussing and challenging two criticisms on coefficient α , the well-known lower bound to test-score reliability, we discuss classical test theory and the theory of coefficient α . The first criticism expressed in the psychometrics literature is that coefficient α is only useful when the model of essential τ -equivalence is consistent with the item-score data. Because this model is highly restrictive, coefficient α is smaller than test-score reliability and one should not use it. We argue that lower bounds are useful when they assess product quality features, such as a test-score’s reliability. The second criticism expressed is that coefficient α incorrectly ignores correlated errors. If correlated errors would enter the computation of coefficient α , theoretical values of coefficient α could be greater than the test-score reliability. Because quality measures that are systematically too high are undesirable, critics dismiss coefficient α . We argue that introducing correlated errors is inconsistent with the derivation of the lower bound theorem and that the properties of coefficient α remain intact when data contain correlated errors.

• Publisher: Springer US,Springer Nature B.V
• Subject: Assessment / Behavioral Science and Psychology / Classical test theory / Cronbach's alpha / Humanities / Law / Psychology / Psychometrics / Reliability / Reproducibility of Results / Revisiting Cronbach’s Alpha / Statistical Theory and Methods / Statistics for Social Sciences / Test Theory / Testing and Evaluation