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DOI: 10.1177/0146621607302479 Nonparametric Person-Fit Analysis of Polytomous Item ScoresTilburg University, w.h.m.emons{at}uvt.nl Person-fit methods are used to uncover atypical test performance as reflected in the pattern of scores on individual items in a test. Unlike parametric person-fit statistics, nonparametric person-fit statistics do not require fitting a parametric test theory model. This study investigates the effectiveness of generalizations of nonparametric person-fit statistics to polytomous item response data. A simulation study using varying test and item characteristics shows that a simple count of the Guttman errors is effective in detecting serious person misfit. The simulation study further shows that in most conditions a simple nonparametric person-fit statistic is as effective as a commonly used parametric person-fit statistic in detecting deviant item score vectors. An empirical example illustrates the use of the nonparametric person-fit statistics in real data.
Key Words: aberrant response behavior nonparametric item response theory person-fit analysis person misfit polytomous items
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