Sixty students were categorized into a stratified four-group design to ascertain the predictive value of achievement motivation as it relates to: (1) diagnostic problem solving ability, (2) diagnostic problem solving knowledge, and (3) student attitude toward the course. Each of the four groups represented varying strengths of achievement motivation following their simultaneous classification as high or low in Achievement and Test Anxiety. The students were also assigned to one of three strata on the basis of scholastic aptitude scores to assure that the four groups were equal in scholastic ability. Two-way analysis of variance technique was used, and Scheffe's "Test for Multiple Comparisons" was also applied when the F-test revealed a significant difference. Conclusions were: (1) The group highest in strength of achievement was statistically superior on both the problem solving performance and the problem solving knowledge variables to the group lowest in strength of achievement, (2) The group with high scholastic ability was also statistically superior on both variables to the group lowest in scholastic ability, and (3) No significant differences were found in attitude scores, either between groups or between the three levels of scholastic ability. This Ed.D. thesis was submitted to the University of Missouri. (GR)