Rater types in writing performance assessments: A classification approach to rater variability

Research on rater effects in language performance assessments has provided ample evidence for a considerable degree of variability among raters. Building on this research, I advance the hypothesis that experienced raters fall into types or classes that are clearly distinguishable from one another with respect to the importance they attach to scoring criteria. To examine the rater type hypothesis, I asked 64 raters actively involved in scoring examinee writing performance on a large-scale assessment instrument to indicate on a four-point scale how much importance they would attach to each of nine routinely used criteria. The criteria covered various performance aspects, such as fluency, completeness, and grammatical correctness. In a preliminary step, many-facet Rasch analysis revealed that raters differed significantly in their views on the importance of the various criteria. A two-mode clustering technique yielded a joint classification of raters and criteria, with six rater types emerging from the analysis. Each of these types was characterized by a distinct scoring profile, indicating that raters were far from dividing their attention evenly among the set of criteria. Moreover, rater background variables were shown to partially account for the scoring profile differences. The findings have implications for assessing the quality of large-scale rater-mediated language testing, rater monitoring, and rater training.