Purpose: This study intended to examine the generalizability and reliability of essay ratings within the scope of the generalizability (G) theory. Specifically, the effect of raters on the generalizability and reliability of students’ essay ratings was examined. Furthermore, variations of the generalizability and reliability coefficients with respect to the number of raters and optimal number of raters for obtaining optimal reliability of the rating of the writing ability of a student, which is considered to be an implicit trait as a whole and in its sub-dimensions of wording/writing, paragraph construction, and title selection, were determined.
Research Methods: The student sample of the study comprised 443 students who were selected via random cluster sampling, and rater sample of this study comprised four Turkish teachers. All the essays written by the students in the sample were independently rated on a writing skill scale (WSS), which is an ordinal scale comprising 20 items, by four trained teachers. In this study, data analysis was performed using the multivariate