Abstract
A method to get Propagation Diagram for friendship is proposed using the sociomatrix obtained from the sociometric test based on interval scale measurement. All names of pupils in the class are written in the sheet. The diagram is a kind of sociogram and is gotten by using the fuzzy structural modeling. The diagram graphically represents group relationships and propagation of friendhips among pupils. A teacher can easily find which pupil may require his/her guidance. The grades of membership of five characteristic values of the diagram in the fuzzy set "small numbers" are defined. It is defined that the grade of unity of a class is equal to the minimum value in their grades of membership. The classes are classified into the two sets, one of which is well united classes and the other lacks unity, by the grade of unity. It is shown that the characteristic values can clearly discriminate between the two sets. A teacher can grasp the changing of friendship by comparing the diagrams and the grades of unity at two points of time. Many teachers favorably estimate that it is very easy and useful to grasp real state in their classes from the diagrams.
