Abstract
Samejima's(1969) graded response model is useful for analyzing test items scored as grade-based. This paper presents two item characteristic curve(item true score) methods of estimating equating coefficients for the item parameters of the graded response model under the common-item design. The first is one in which the criterion function is defined on the both target and new scales like the Haebara's criterion function for the dichotomous response model. The second is one in which the criterion function is defined only on the target scale. The results of simulation experiments, which implemented horizontal and vertical equatings, suggest that the item characteristic curve, the test characteristic curve and the Mean & Sigma methods are preferable to the category characteristic curve and the Mean & Mean methods in terms of standard errors.
