To evaluate reliability or precision with respect to a data mining result and to quantitatively evaluate factors of a secondary effect and after.

A rule existing among plural data is extracted by data mining, and the rule and information expressing the reliability of the rule are outputted. A group division evaluation value S ratio and t value expressing the clarity of division at the time of halving a group consisting of plural data are defined as information expressing the reliability of the rule as shown by equations (1) and (2) when S ratio={(S1+S2)/2)}/S0 and the distribution of the divided group has any significant difference. In the equations (1) and (2), S0 denotes the sum of squares of the target variable of the group before division, and S1 and S2 the sum of squares of the target variables in each group after division, and N1 and N2 the number of element, and X1' and X2' are averages. In this case, according as the value of the S ratio is small, or the value of the t value is large, the division of the group is clearly performed.