Creating a Test Information Profile for a Two-Dimensional Latent Space

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Abstract
In some cognitive testing situations it is believed, despite reporting only a single score, that the test items differentiate levels of multiple traits. In such situa tions, the reported score may represent quite disparate composites of these multiple traits. Thus, when attempting to interpret a single score from a set of multidimensional items, several concerns naturally arise. First, it is important to know what composite of traits is being measured at all levels of the reported score scale. Second, it is also necessary to discern that all examinees, no matter where they lie in the latent trait space, are being measured on the same composite of traits. Thus, the role of multidimensionality in the interpretation or meaning given to various score levels must be examined. This paper presents a method for computing multidimensional information and provides examples of how different aspects of test information can be displayed graphically to form a profile of a test in a two-dimensional latent space. Index terms: information, item response theory, multidimensional item response theory, test information.