A COMPARISON OF EQUAL PERCENTILE AND PARTIAL CREDIT EQUATINGS FOR PERFORMANCE-BASED ASSESSMENTS COMPOSED OF FREE-RESPONSE ITEMS

This study compares the equal percentile (EP) and partial credit (PC) equatings for raw scores derived from performance-based assessments co mposed of free-response (open-ended) items clustered around long readi ng selections or multistep mathematics problems. Data are from the Mar yland School Performance Assessment Program. The results suggest that Masters' (1982; Wright & Masters, 1982) partial credit model may be us eful for equating examinations composed of moderately easy (or not too difficult) items sharing a first principal component with at least 25 % of the total variance. This conclusion appears to hold even in the p resence of some level of response dependency for the items within each cluster. Although visible discrepancies were found between PC and EP equated scores in the skewed tail of the score distributions, the dire ction of these discrepancies is unpredictable. Therefore, it cannot be concluded from the study that the two methods give equivalent results when the distributions are markedly skewed.