Browsing by Author "Molenaar, Ivo W."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Reliability estimation for single dichotomous items based on Mokken's IRT model
    (1995) Meijer, Rob R.; Sijtsma, Klaas; Molenaar, Ivo W.
    Item reliability is of special interest for Mokken’s nonparametric item response theory, and is useful for the evaluation of item quality in nonparametric test construction research. It is also of interest for nonparametric person-fit analysis. Three methods for the estimation of the reliability of single dichotomous items are discussed. All methods are based on the assumptions of nondecreasing and nonintersecting item response functions. Based on analytical and monte carlo studies, it is concluded that one method is superior to the other two, because it has a smaller bias and a smaller sampling variance. This method also demonstrated some robustness under violation of the condition of nonintersecting item response functions. Index terms: item reliability, item response theory, Mokken model, nonparametric item response models, test construction.
  • Thumbnail Image
    Item
    Selection of unidimensional scales from a multidimensional item bank in the polytomous Mokken IRT model
    (1995) Hemker, Bas T.; Sijtsma, Klaas; Molenaar, Ivo W.
    An automated item selection procedure for selecting unidimensional scales of polytomous items from multidimensional datasets is developed for use in the context of the Mokken item response theory model of monotone homogeneity (Mokken & Lewis, 1982). The selection procedure is directly based on the selection procedure proposed by Mokken (1971, p. 187) and relies heavily on the scalability coefficient H (Loevinger, 1948; Molenaar, 1991). New theoretical results relating the latent model structure to H are provided. The item selection procedure requires selection of a lower bound for H. A simulation study determined ranges of H for which the unidimensional item sets were retrieved from multidimensional datasets. If multidimensionality is suspected in an empirical dataset, well-chosen lower bound values can be used effectively to detect the unidimensional scales. Index terms: item response theory, Mokken model, multidimensional item banks, nonparametric item response models, scalability coefficient H, test construction, unidimensional scales.