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Relationship Between Performance on the NBME Comprehensive Basic Sciences Self-Assessment and USMLE Step 1 for U.S. and Canadian Medical School Students

Morrison, Carol A.; Ross, Linette P.; Fogle, Thomas; Butler, Aggie; Miller, Judith; Dillon, Gerard F.

Section Editor(s): Hess, Brian PhD; Hawkins, Richard MD

doi: 10.1097/ACM.0b013e3181ed3f5c
Predictive Validity and High-Stakes Exams

Background This study examined the relationship between performance on the National Board of Medical Examiners Comprehensive Basic Science Self-Assessment (CBSSA) and performance on United States Medical Licensing Examination Step 1.

Method The study included 12,224 U.S. and Canadian medical school students who took CBSSA prior to their first Step 1 attempt. Linear and logistic regression analyses investigated the relationship between CBSSA performance and performance on Step 1, and how that relationship was related to interval between exams.

Results CBSSA scores explained 67% of the variation in first Step 1 scores as the sole predictor variable and 69% of the variation when time between CBSSA attempt and first Step 1 attempt was also included as a predictor. Logistic regression results showed that examinees with low scores on CBSSA were at higher risk of failing their first Step 1 attempt.

Conclusions Results suggest that CBSSA can provide students with a realistic self-assessment of their readiness to take Step 1.

Correspondence: Carol A. Morrison, PhD, 3750 Market Street, Philadelphia, PA 19104; e-mail:

© 2010 Association of American Medical Colleges