What factors impact student performance in introductory physics?

In a previous study, we found that students' incoming preparation in physics-crudely measured by concept inventory prescores and math SAT or ACT scores-explains 34% of the variation in Physics 1 final exam scores at Stanford University. In this study, we sought to understand the large variation in exam scores not explained by these measures of incoming preparation. Why are some students' successful in physics 1 independent of their preparation? To answer this question, we interviewed 34 students with particularly low concept inventory prescores and math SAT/ACT scores about their experiences in the course. We unexpectedly found a set of common practices and attitudes. We found that students' use of instructional resources had relatively little impact on course performance, while student characteristics, student attitudes, and students' interactions outside the classroom all had a more substantial impact on course performance. These results offer some guidance as to how instructors might help all students succeed in introductory physics courses.