With reference to FIGS. 1 and 13, in the method for indicating characteristic of problem set according to the fifth embodiment of the present invention, the marking result with respect to the problem set can be provided in the step of visualizing characteristic of problem set (S40) or in its prior steps. That is, when a specific learner solves a plurality of problems included in a problem set, the marking result according to the solving result can be provided.

According to this, with reference to FIG. 14, in the step of visualizing determined characteristic of problem set, correlations between attributes related with a problem, to which a learner made a right solution can be displayed as a line differently from a line representing correlations between attributes related with a problem, to which a learner made a wrong solution. Here, the appearance of a line means thickness, shape, color, or the like, but is not limited thereto.

For example, the correlations between attributes related with the third problem, which is found to be right solution according to the marking result, can be displayed as a blue line. Also, the correlations between attributes related with the first problem, which is found to be wrong solution according to the marking result, can be displayed as a red line. It should be noted that the color of a line corresponding to the correlation related with the problem of right solution only needs to be different from that of a line corresponding to the correlation related with the problem of wrong solution, thus the color is not limited to blue or red.