ADDITIVITY OF TEST ITEMS DIFFICULTIES

The impartial analysis shows: the theory IRT and related parametric models of difficulty of test items of Rush and Birnbaum does not possess natural additivity property even at the level of definitions. At the same time, in the framework of proposed earlier by author a new model of testing the additivity of test items difficulties not only stems from the definition, but also allows an empirical test with the help of specially created for this purpose the method of virtual testing. The results of validation confirm the adequacy of the new model.