Understanding a Widely Misunderstood Statistic: Cronbach's "Alpha"

It is important to explore score reliability in virtually all studies, because tests are not reliable. The present paper explains the most frequently used reliability estimate, coefficient alpha, so that the coefficient's conceptual underpinnings will be understood. Researchers need to understand score reliability because of the possible impact reliability has on the interpretation of research results. There are several common misconceptions about the basic ideas of score reliability. Misconceptions are formed due to lack of understanding of the concept of reliability and through careless speech involving statistical jargon. This paper addresses common misconceptions so that later discussions over score reliability will not be hindered. Misconceptions have caused some authors to devalue the reporting of reliability estimates in published research, while others report reliability coefficients inappropriately. A better understanding of score reliability can resolve these misconceptions and enable authors to use reliability coefficients appropriately in literature and speech. A background of the basic ideas of score reliability is introduced and concludes with an explanation of the most frequently used reliability estimate, coefficient alpha, so that the coefficient's conceptual underpinnings will be understood. (Contains 6 tables.)