Test administrators are appropriately concerned about the potential for time constraints to impact the validity of score interpretations; psychometric efforts to evaluate the impact of speededness date back more than half a century. The widespread move to computerized test delivery has led to the development of new approaches to evaluating how examinees use testing time and to new metrics designed to provide evidence about the extent to which time limits impact performance. Much of the existing research is based on these types of observational metrics; relatively few studies use randomized experiments to evaluate the impact time limits on scores. Of those studies that do report on randomized experiments, none directly compare the experimental results to evidence from observational metrics to evaluate the extent to which these metrics are able to sensitively identify conditions in which time constraints actually impact scores. The present study provides such evidence based on data from a medical licensing examination. The results indicate that these observational metrics are useful but provide an imprecise evaluation of the impact of time constraints on test performance.