Two approaches to equating, the common item equating method (weighted and unweighted) and the one-step, missing data calibration method, used with Rasch (1960/1980) measurement models are compared. The data used in the analysis were taken from six equivalent forms of a perceptual ability test administered as part of the Dental Admission Test. Simulated data patterned after the observed item difficulties were also analyzed to form a frame of reference against which to judge the accuracy of the equating. The results indicate that there is very little difference among the three methods of equating even in the presence of measurement disturbances such as guessing.
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