Clarifying the contribution of assessee-, dimension-, exercise-, and assessor-related effects to reliable and unreliable variance in assessment center ratings.

Though considerable research has evaluated the functioning of assessment center (AC) ratings, surprisingly little research has articulated and uniquely estimated the components of reliable and unreliable variance that underlie such ratings. The current study highlights limitations of existing research for estimating components of reliable and unreliable variance in AC ratings. It provides a comprehensive empirical decomposition of variance in AC ratings that: (a) explicitly accounts for assessee-, dimension-, exercise-, and assessor-related effects, (b) does so with 3 large sets of operational data from a multiyear AC program, and (c) avoids many analytic limitations and confounds that have plagued the AC literature to date. In doing so, results show that (a) the extant AC literature has masked the contribution of sizable, substantively meaningful sources of variance in AC ratings, (b) various forms of assessor bias largely appear trivial, and (c) there is far more systematic, nuanced variance present in AC ratings than previous research indicates. Furthermore, this study also illustrates how the composition of reliable and unreliable variance heavily depends on the level to which assessor ratings are aggregated (e.g., overall AC-level, dimension-level, exercise-level) and the generalizations one desires to make based on those ratings. The implications of this study for future AC research and practice are discussed.