Delimiting Coefficient α from Internal Consistency and Unidimensionality. Issue 4 (6th November 2015)

• Record Type: Journal Article
• Authors: Sijtsma, Klaas
• Is Part Of: Educational measurement. Volume 34:Issue 4(2015:Winter)
• Page Start: 10
• Page End: 13
• Publication Date: 2015-11-06
• Subjects: coefficient α -- internal consistency -- reliability -- unidimensionality -- validity; Educational tests and measurements -- Periodicals; Educational tests and measurements -- United States -- Periodicals; 371.262
• DOI: 10.1111/emip.12099
• Languages: English
• ISSNs: 0731-1745

Abstract

Abstract : I discuss the contribution by Davenport, Davison, Liou, & Love (2015) in which they relate reliability represented by coefficient α to formal definitions of internal consistency and unidimensionality, both proposed by Cronbach (1951). I argue that coefficient α is a lower bound to reliability and that concepts of internal consistency and unidimensionality, however defined, belong to the realm of validity, viz. the issue of what the test measures. Internal consistency and unidimensionality may play a role in the construction of tests when the theory of the attribute for which the test is constructed implies that the items be internally consistent or unidimensional. I also offer examples of attributes that do not imply internal consistency or unidimensionality, thus limiting these concepts' usefulness in practical applications.