In Nohda (1998), a model in the form of a matrix has been constructed to evaluate responses by the criteria of "diversity"and "generality." In the matrix,an item (Aij) shows the number of responses by the student."Diversity" is expressed by (Aij) where j is a constant,in which different mathematical ideas correspond to different (Aij). "Generality"is expressed by (Aij) where i is a constant, in which different level of generality correspond to different (Aij). For instance, responses of "marble problem"described above can be evaluated in the following way.