AN ITEM RESPONSE THEORY ANALYSIS OF THE GENERAL AND ACADEMIC SCALES OF THE SELF-DESCRIPTION QUESTIONNAIRE-II

The psychometric properties of four Self-Description Questionnaire II scales (SDQII; Marsh, 1990) were analyzed in a sample of eighth graders (N = 1,141). Specifically, item response theory (IRT) techniques were used to study the bandwidth-fidelity and gender equivalence of the SDQII General, School, Math, and Verbal scales. Findings indicated that the SDQII scales have peaked test information curves, providing excellent discrimination among examinees who are low or moderate in self-concept. Several items, however, appear to be redundant in terms of the psychometric information they provide, indicating that the measures could be shortened. Results also revealed that with few exceptions, the SDQII items function equivalently across genders. Implications are discussed in terms of self-concept measurement and, more generally, in terms of IRT analysis of personality scale item responses. (C) 1995 Academic Press, Inc.