Ramsay-Curve Item Response Theory for the Three-Parameter Logistic Item Response Model  

Oleh:

Woods, Carol M.

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: Applied Psychological Measurement vol. 32 no. 6 (Sep. 2008), page 447-465.
Topik: Ramsay curve; RC-IRT; normality assumption; 3PL model; empirical histogram
Fulltext: 447.pdf (364.73KB)

Isi artikel

In Ramsay-curve itemresponse theory (RC-IRT), the latent variable distribution is estimated simultaneously with the item parameters of a unidimensional itemresponse model using marginal maximum likelihood estimation. This study evaluates RC-IRT for the three-parameter logistic (3PL)modelwith comparisons to the normal model and to the empirical histogram method (EHM) implemented in BILOG-MG. Results support the validity and utility of RC-IRT for the 3PLmodel. RC-IRT and the EHMboth performed better than the normalmodel for nonnormal latent distributions and appeared to have complementary strengths. Item parameter estimates tended to be more accurate with the EHM, especially for shorter tests; however, recovery of the latent distribution was better, and scoreswere less biased, with RCIRT. Differences between RC-IRT and the EHM diminished as the sample size and especially the test length increased. Practical recommendations for estimating the latent distribution with the 3PLmodel are provided.

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