Effects of Using Double Ratings as Item Scores on IRT Proficiency Estimation

ABSTRACT This article presents the performance of item response theory (IRT) models when double ratings are used as item scores over single ratings when rater effects are present. Study 1 examined the influence of the number of ratings on the accuracy of proficiency estimation in the generalized partial credit model (GPCM). Study 2 compared the accuracy of proficiency estimation of two IRT models (GPCM versus the hierarchical rater model, HRM) for double ratings. The main findings were as follows: (a) rater effects substantially reduced the accuracy of IRT proficiency estimation; (b) double ratings relieved the negative impact of rater effects on proficiency estimation and improved the accuracy relative to single ratings; (c) IRT estimators showed different patterns in the conditional accuracy; (d) as more items and a larger number of score categories were used, the accuracy of proficiency estimation improved; and (e) the HRM consistently showed better performance than the GPCM.