The impact of rater effects on weighted composite scores under nested and spiraled scoring designs, using the multifaceted Rasch model.

Constructed-response or open-ended tasks are increasingly used in recent years. Since these tasks cannot be machine-scored, variability among raters cannot be completely eliminated and their effects, when they are not modeled, can cast doubts on the reliability of the results. Besides rater effects, the estimation of student ability can also be impacted by differentially weighted tasks/items that formulate composite scores. This simulation study compares student ability estimates with their true abilities under different rater scoring designs and differentially weighted composite scores. Results indicate that the spiraled rater scoring design without modeling rater effects works as well as the nested design in which rater tendencies are modeled. As expected, differentially weighted composite scores have a confounding effect on student ability estimates. This is particularly true when open-ended tasks are weighted much more than the multiple-choice items and when rater effects interact with weighted composite scores.