EDUCATIONAL AND PSYCHOLOGICAL MEASUREMENT

The interaction of mental ability and two instructional methods (instructor-paced guided discovery and student-paced mastery learn-ing) was investigated for a second grade linear metric curriculum unit. As predicted, mental ability was positively (r =.71) correlated with achievement for students (N = 47) taught by the guided discov-ery method, but mental ability was essentially uncorrelated (r =.12) with achievement on the metric unit for students (N = 55) taught by the mastery learning method. Areas of significant differences were found using multiple regression methods and the Johnson-Neyman technique. The implications of the trait X treatment interaction found in this study were discussed with respect to instructional theory and the prediction of academic achievement