APPLICATION OF ITEM RESPONSE THEORY TO PSYCHOLOGICAL TEST CONSTRUCTION

Ana Stojanov

Abstract


In the first part of this paper the shortcomings of classical test theory, such as test-centeredness, dependence of parameter estimates on the sample used and the assumption that the test discriminates equally among all participants, are presented. In the second part, item response theory is offered as an alternative to classical test theory. Here, the basic concepts in item response theory are discussed (category characteristic curve, item information function, test information function, as well as the basic assumptions of item response theory: the assumption of unidimensionality and local independence of items) with particular focus on polytomous models. In the last part the use of item response theory is demonstrated for selection of Likert type items during test construction, but the same principles can be used in constructing a shorter version of an existing questionnaire. 

Key words: classical test theory, Likert type items, psychometrics, item response theory, polytomous models


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