Critiques of coefficient alpha as an estimate of scale reliability are widespread in the literature. However, the continuous overuse of this statistic in mathematics education research suggests a disconnection between theory and practice. As such, this article argues, in a non-technical way, for the limited usefulness of coefficient alpha, its overuse, and its alternatives in estimating scale reliability. Coefficient alpha gives information only about the degree of the interrelatedness of a set of items that measures a construct. Contrary to the widely circulated misconceptions in mathematics education research, a high coefficient alpha value does not mean the instrument is reliable, and it does not imply the instrument measures a single construct. Coefficient alpha can only be dependable as an estimate of reliability under verifiable and restrictive conditions. I expose these conditions and present steps for their verification in empirical studies. I discuss some alternatives to coefficient alpha with references to non-technical articles where worked examples and programming codes are available. I hope this exposition will influence the practices of mathematics education researchers regarding estimation of scale reliability.
Keywords: Cronbach’s alpha; internal consistency; reliability coefficient; research instrument; unidimensionality.
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