ABSTRACT
In addition to affecting the reliability coefficient of a test, the heterogeneity of the group tested will also affect the validity coefficient. For example, if in Figure 1 the abscissa represents a test and the ordinate a criterion, the validity coefficient for the total group will be much greater than the validity coefficient for the restricted portion of the group included between the two dotted lines. The validity coefficient would be lowered in a similar manner if the selection were made upon the basis of the criterion variable.
