The Objective Borderline method (OBM): A probability-based model for determining an objective Pass/Fail cut-off score for Borderline grades

The decision to pass or fail a student is the most critical in ‘high stakes’ examinations. This study introduces and validates a new probabilistic-based standard-setting method for determining the pass/fail cut-off score from borderline grades named the Objective Borderline method (OBM). The OBM sets up the cut-score based on the distribution of the Pass, Borderline and Fail grades within a given examination. Three methods for setting up pass/fail cut-off scores were compared: the Regression Method, the Borderline Group Method, and the new Objective Borderline Method (OBM). We used ’Objective Structured Clinical Examination’ (OSCE) results from one medical school in New Zealand to establish the pass/fail cut-off scores by the abovementioned three methods. The results indicate that the pass/fail cut-off scores generated by the OBM were similar to those generated by the more established methods (0.840 < r < 0.998; p<.0001). Based on theoretical and empirical analysis, we suggest that the OBM has advantages over existing methods in that it combines objectivity, realism, robust empirical basis and is simple to use. Moreover, although demonstrated within clinical assessment context, some simulated studies (unpublished) demonstrated that the OBM is context free and is applicable across almost any context with very few limitations.