The purpose of this semester-long study was to investigate the effect of replacing traditional lectures with cooperative group problem-solving sessions in a junior-level quantitative analysis course. The control and treatment groups had the same instructor, met on the same day, had the same reading assignments, and had common exams. The instructor worked on sample problems for the control group. In the treatment group, students were assigned to heterogeneous cooperative groups of 4. The groups solved problems presented on an overhead that were the same or equivalent in content and number to those used in the control group. Students were responsible for making sure that all members of the group could work on each problem. The student’s reasoning abilities were measured by the Test of Logical Thinking (TOLT). Groups were compared on quizzes, exams, finals, and course grades. Other data included attitudinal surveys, observations, field notes, interviews, and open-response evaluations. No significant differences were found in content measures. Differences were found in the number of students dropping the course and in the attitudes and perceptions of the two groups. Qualitative measures support a number of assertions concerning more positive attitudes and lower withdrawal rates in the treatment group, and a case for mixed delivery modes.
One consistent message from survey respondents was that the number of students who drop their course was significantly lower in classes taught using PI than in classes taught using a more traditional pedagogy. This is consistent with data from other studies, such as that of Williamson and Rowe  who reported a 33.3% withdrawal rate from a traditional (control) class but only 17.3% from the treatment section in which lecture was replaced with cooperative group problem-solving. Instructors also remarked that student performance, overall, was better when using PI.
The class learning environment changes when PI is adopted. This is again consistent with Williamson and Rowe  who report that courses taught using an interactive pedagogy display better communication between instructor and students and an increased tendency for students to ask questions in class. A survey respondent teaching physics at a Southern university reported that “students talked a lot more during class and asked many more questions than they usually do, even when we were not doing the [PI] discussions.”