Investigation of IRT-Based Equating Methods in the Presence of Outlier Common Items  

Oleh:

Huiqin, Hu ; Rogers, W. Todd ; Vukmirovic, Zarko

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: Applied Psychological Measurement vol. 32 no. 4 (Jun. 2008), page 311-333.
Topik: item response theory; equating; outliers; calibration; transformation
Fulltext: 311.pdf (183.45KB)

Isi artikel

Common items with inconsistent b-parameter estimates may have a serious impact on item response theory (IRT)–based equating results. To find a better way to deal with the outlier common items with inconsistent b-parameters, the current study investigated the comparability of 10 variations of four IRT-based equating methods (i.e., concurrent calibration, separate calibration with test characteristic curve [TCC] and mean/sigma [M/S] transformations, and calibration with fixed common item parameters [FCIP]) when outliers were either ignored or considered. Simulated data were generated for the common-item nonequivalent groups matrix design to reflect themanipulated factors: group ability differences and nonequivalent groups, number/score points of outliers, and types of outliers. When no outliers were present, the TCC and M/S transformations performed the best.When there were outliers, overall, the methods that considered them (except theM/S transformation with outliers weighted) resulted in a vast improvement compared to the methods that ignored them.

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