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An Investigation of the Feasibility of Applying Item Response Theory to Equate Achievement Tests ATP GRE IRT

Cook, Linda L.; Eignor, Daniel R.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Achievement Tests, Admissions Testing Program (ATP), Equated Scores, Graduate Record Examinations (GRE), Item Response Theory (IRT), Scaling


The purpose of this study was to examine the feasibility of using item response theory (IRT) procedures to equate different forms of three achievement tests (Biology, American History and Social Studies, and Mathematics Level II) that are administered by the College Board Admissions Testing program and one achievement test (Advanced Biology) that is part of the Graduate Record Examinations Achievement Test battery. All of the tests investigated in this study are typically equated using conventional linear or curvilinear (equipercentile) methods. The results of the study indicate, using scale drift as the evaluative criterion, that it is feasible to use item response theory to equate the four Achievement tests selected for investigation. The results also indicate that the conventional linear methods typically used to equate the tests perform quite adequately. The question of whether the IRT procedures used in the study are sufficiently robust to violations of the assumption of unidimensionality, or whether Achievement tests, of the type used in this study, give rise to sufficiently unidimensional data, must be resolved before the results of the study can be generalized to other Achievement testing situations. (99pp.)

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