Semantic errors in aphasia (e.g., naming a horse as "dog") frequently arise from faulty mapping of concepts onto lexical items. A recent study by our group used voxel-based lesion-symptom mapping (VLSM) methods with 64 patients with chronic aphasia to identify voxels that carry an association with semantic errors. The strongest associations were…

Missing data are a pervasive problem in many psychological applications in the real world. In this article we study the impact of dropout on the operational characteristics of several approaches that can be easily implemented with commercially available software. These approaches include the covariance pattern model based on an unstructured…

A multi-faceted Rasch measurement (MFRM) model was used to analyze a clinical skills assessment of 173 fourth-year medical students in a Midwestern medical school to investigate four types of rater errors: leniency, inconsistency, halo, and restriction of range. Each student performed six clinical tasks with six standardized patients (SPs), who…