Purpose: Many factors influence the reliable assessment of medical students' competencies in the clerkships. The purpose of this study was to determine how many clerkship competency assessment scores were necessary to achieve an acceptable threshold of reliability.
Method: Clerkship student assessment data were collected during the 2015-2016 academic year as part of the medical school assessment program at the University of Michigan Medical School. Faculty and residents assigned competency assessment scores for third-year core clerkship students. Generalizability (G) and decision (D) studies were conducted using balanced, stratified, and random samples to examine the extent to which overall assessment scores could reliably differentiate between students' competency levels both within and across clerkships.
Results: In the across-clerkship model, the residual error accounted for the largest proportion of variance (75%), whereas the variance attributed to the student and student-clerkship effects was much smaller (7% and 10.1%, respectively). D studies indicated that generalizability estimates for eight assessors within a clerkship varied across clerkships (G coefficients range = 0.000-0.795). Within clerkships, the number of assessors needed for optimal reliability varied from 4 to 17.
Conclusions: Minimal reliability was found in competency assessment scores for half of clerkships. The variability in reliability estimates across clerkships may be attributable to differences in scoring processes and assessor training. Other medical schools face similar variation in assessments of clerkship students; therefore, the authors hope this study will serve as a model for other institutions that wish to examine the reliability of their clerkship assessment scores.