| Research Abstract |
In this research, equating methods for the gereralized partial credit model(Muraki,1992) based on common item design were presented. The first method, called Mean &; Mean method, estimated equating coefficients by functions of arithmetic means of item parameter estimates. The second and third methods, called normit chi-squares methods, estimated these coefficients by the weighted least squares method with the item parameter estimates and/or standard errors. The fourth and fifth methods, called item characteristic methods, used the error functions defined by Haebara(1980). The sixth and seventh methods, called true score methods, equated tests using the functions defiend by Stocking ＆ Lord(1982) which used true scores. Simulations are performed in which equating coefficients were estimated by the seven methods on both horizontal and vertical equating conditions. The results indicated that these seven methods perform well. FORTRAN executable program for equating tests under the generalized partial credit model developed in this research will be distributed via WEB site.
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