The present study evaluated the effectiveness of two different systems of instruction, the traditional method and the phase achievement method, and their relationship to different informational variables--use of lectures, textbooks, study guides and video cassette tapes provided for students in a college biology course at Iowa State University. The phase achievement method is a self-paced instructional system which shares some common elements with a personalized system of instruction (PSI), and Bloom's mastery strategy. In this system, learning objectives must be clearly defined, selected, and organized into relatively small units to help students as a guide and to provide levels for mastery. The students' final grades were based on passing a minimum number of unit tests successfully, regardless of the order of the units, with the minimum score on each unit combined with a final exam score to reach the final grade. The unit tests played a major diagnostic role in assisting students. The main difference between this system and the traditional method, in this study, was in the testing and the grading policies;Data used in the present study had been gathered by NSF-CAUSE project personnel on 216 students in the traditional section of Biology 101 in the fall of 1978 and compared to data from 147 students in the phase achievement section of the same course during the same quarter. The investigation sought answers to three main questions: (1) total amount of time required for course completion in either section; (2) the best combination of study patterns for grade prediction in either section; and (3) the relationship between different levels of student abilities, the science backgrounds of the students, and their subsequent achievements;By the use of the General Linear Model and Residual Analysis, the results of this study indicated that there was no significant difference between sections with regard to the first question. Use of textbooks, study guides, and lecture notes seemed to be more helpful for students in the traditional section, while videotapes, textbooks, and study guides worked best for students in the phase achievement section. No significant difference was found when comparing students with high abilities and high level backgrounds between the two sections. A similar result was found for those with low abilities and low level backgrounds. For students with high abilities but low level backgrounds, the phase achievement system appeared to be more beneficial.