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Delimiting Coefficient α from Internal Consistency and Unidimensionality
Author(s) -
Sijtsma Klaas
Publication year - 2015
Publication title -
educational measurement: issues and practice
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.158
H-Index - 52
eISSN - 1745-3992
pISSN - 0731-1745
DOI - 10.1111/emip.12099
Subject(s) - cronbach's alpha , internal consistency , consistency (knowledge bases) , reliability (semiconductor) , realm , psychology , social psychology , test (biology) , econometrics , statistics , mathematics , psychometrics , political science , discrete mathematics , paleontology , power (physics) , physics , quantum mechanics , biology , law
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.