NBME subject examinations provide medical schools with a tool for measuring students' understanding of the clinical sciences. While subject examinations are designed to be appropriate for use by most medical schools, curricular objectives vary, and the congruence between subject examination content and curricular objectives should be considered in the interpretation of test scores and in the determination of grading and promotion standards. NBME neither sets nor recommends a “passing” score.  Subject examination scores should not be used alone, but rather in conjunction with other indicators of student performance.

Subject Examination Scores

The subject examination score on the Comprehensive Clinical Science Examination (CCSE) is scaled so that a score of 70 on the CCSE is approximately equivalent to a score of 200 on USMLE® Step 2 Clinical Knowledge (CK). The vast majority of scores range from 45 to 95, and although the scores have the "look and feel" of percent-correct scores, they are not. Because the CCSE and USMLE Step 2 CK cover similar content, this scale provides a useful tool for comparing the scores of your students with those of a large, nationally representative group taking the licensing exam in their final year of medical school.  Additional information about the relationship between CCSE scores and USMLE Step 2 CK scores is provided in the table on the next page.

Unlike percent-correct scores, subject examination scores on the CCSE are statistically equated across test administrations. As a result, these scores can be used to track student performance over time.

Precision of Scores

Measurement error is present on all tests, and the standard error of measurement (SEM) provides an index of the (im)precision of scores.  The SEM indicates how far the score a student earns on the examination is likely to stray from his/her “true” proficiency level. The SEM is approximately 4 points for the CCSE scores. Using the SEM, it is possible to calculate a score interval that indicates how much a score might vary across repeated testing using different sets of items covering the same content.  An interval that will encompass about two thirds of the observed scores for a given true score may be found by adding the SEM to a score and subtracting it from that score.  For example, if a student’s true proficiency on the examination is 60, the score he/she achieved on the examination will usually (two times out of three) fall between 56 and 64  (60 - 4 and 60 + 4)

Approximate USMLE® Performance Equivalents

The table to the right provides approximate performance equivalents for USMLE Step 2 CK, making it possible for you to translate the CCSE scores of your students to the scale used for USMLE Step 2 CK. Specific information on USMLE Step 2 CK and the current minimum passing score is available on the web site for USMLE® (http://www.usmle.org).

To use the table, locate a student's CCSE score in the associated column and note the entry in the column labeled "Step 2 CK Equivalent". For example, if a student's score is 60, the corresponding entry of 175 indicates that the student's performance on the CCSE is approximately equivalent to a Step 2 CK score of 175.

Note: This examination is not intended to predict performance on USMLE.  Rather, it is intended to be used to determine a student’s relative areas of strength and weakness in general topic areas.

             Approximate Step 2 CK Equivalents