This study illustrates how a factor analysis of a well-designed student-rating instrument can increase its utility. Factor analysis of a student-rating instrument was used to reveal constructs that would explain student attrition in science, mathematics, and engineering majors. The Instructional Development and Effectiveness Assessment (IDEA) instrument is used to rate college courses in science or mathematics at Kansas State University. It is used to gather students' reactions to instructors, personal progress, and courses, as well as students' attitudes, and to obtain an overall rating. Subjects for the factor analysis were 141 upperclass students (56.7 percent male). The factor analysis reveals constructs about which students in science and mathematics have expressed concern. Of seven identified factors, the first three, interpreted as instructor presentation skills, student perception of personal progress, and student-teacher interaction, are particularly important in distinguishing instructor presentation from the personal aspects of course takers. Three tables present analysis results. (Contains 23 references.) (SLD)