Abstract
In this paper, a theoretical index of dimensionality, called the theoretical DETECT index, is proposed to provide a theoretical foundation for the DETECT procedure. The purpose of DETECT is to assess certain aspects of the latent dimensional structure of a test, important to practitioner and research alike. Under reasonable modeling restrictions referred to as “approximate simple structure”, the theoretical DETECT index is proven to be maximized at thecorrect dimensionality-based partition of a test, where the number of item clusters in this partition corresponds to the number of substantivelyseparate dimensions present in the test and by “correct” is meant that each cluster in this partition contains only items that correspond to the same separate dimension. It is argued that the separation into item clusters achieved by DETECT is appropriate from the applied perspective of desiring a partition into clusters that are interpretable as substantively distinct between clusters and substantively homogeneous within cluster. Moreover, the maximum DETECT index value is a measure of the amount of multidimensionality present. The estimation of the theoretical DETECT index is discussed and a genetic algorithm is developed to effectively execute DETECT. The study of DETECT is facilitated by the recasting of two factor analytic concepts in a multidimensional item response theory setting: a dimensionally homogeneous item cluster and an approximate simple structure test.
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Portions of this article were presented at the annual meeting of the National Council on Measurement in Education, New York, April 1996.
The authors would like to thank Ting Lu, Ming-mei Wang, and four anonymous reviewers for their comments and suggestions on an earlier version of this manuscript. The research of the first author was partially supported by an ETS/GREB Psychometric Fellowship, and by Educational Testing Service Research Allocation Projects 794-33 and 883-05. The research of the second author was partially supported by NSF grants DMS 94-04327 and DMS 97-04474.
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Zhang, J., Stout, W. The theoretical detect index of dimensionality and its application to approximate simple structure. Psychometrika 64, 213–249 (1999). https://doi.org/10.1007/BF02294536
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DOI: https://doi.org/10.1007/BF02294536