Browsing by Author "Rogers, H. Jane"

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    An assessment of Stout's index of essential unidimensionality
    (1996) Hattie, John; Krakowski, Krzysztof; Rogers, H. Jane; Swaminathan, Hariharan
    A simulation study was conducted to evaluate the dependability of Stout’s T index of unidimensionality as used in his DIMTEST procedure. DIMTEST was found to dependably provide indications of unidimensionality, to be reasonably robust, and to allow for a practical demarcation between one and many dimensions. The procedure was not affected by the method used to identify the initial subset of unidimensional items. It was, however, found to be sensitive to whether the multidimensional data arose from a compensatory model or a partially compensatory model. DIMTEST failed when the matrix of tetrachoric correlations was non-Gramian and hence is not appropriate in such cases. Index terms: DIMTEST, essential unidimensionality, factor analysis, item response models, Stout’s test of unidimensionality, tetrachoric correlations, unidimensionality.
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    A comparison of logistic regression and Mantel-Haenszel procedures for detecting differential item functioning
    (1993) Rogers, H. Jane; Swaminathan, Hariharan
    The Mantel-Haenszel (MH) procedure is sensitive to only one type of differential item functioning (DIF). It is not designed to detect DIF that has a nonuniform effect across trait levels. By generalizing the model underlying the MH procedure, a more general DIF detection procedure has been developed (Swaminathan & Rogers, 1990). This study compared the performance of this procedure-the logistic regression (LR) procedure-to that of the MH procedure in the detection of uniform and nonuniform DIF in a simulation study which examined the distributional properties of the LR and MH test statistics and the relative power of the two procedures. For both the LR and MH test statistics, the expected distributions were obtained under nearly all conditions. The LR test statistic did not have the expected distribution for very difficult and highly discriminating items. The LR procedure was found to be more powerful than the MH procedure for detecting nonuniform DIF and as powerful in detecting uniform DIF. Index terms: differential item functioning, logistic regression, Mantel-Haenszel statistic, nonuniform DIF, uniform DIF.
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    A Monte Carlo investigation of several person and item fit statistics for item response models
    (1987) Rogers, H. Jane; Hattie, John
    This study investigated the behavior of several person and item fit statistics commonly used to test and obtain fit to the one-parameter item response model. Using simulated data for 500 persons and 15 items, the sensitivity of the total-t, mean-square residual, and between-t fit statistics to guessing, heterogeneity in discrimination parameters, and multidimensionality was examined. Additionally, 25 misfitting persons and a misfitting item were generated to test the power of the three fit statistics to detect deviations in a subset of observations. Neither the total-t nor the mean-square residual were able to detect deviation from any of the models fitted. Use of these statistics appears to be unwarranted. The between-t was a useful indicator of guessing and heterogeneity in discrimination parameters, but was unable to detect multidimensionality. These results show that use of person and item fit statistics to test and obtain overall fit to the one-parameter model can lead to acceptance of the model even when it is grossly inappropriate. Assessments of model fit based on this strategy are inadequate. Alternative methods must be sought.