- The effects of increasing class size on student outcomes and persistence is analyzed in online courses.
- A quasi-random field experiment in conjunction with a fixed-effects strategy provides plausibly credible causal estimates.
- Small online class size changes do not lead to differences in student performance as measured by grades or persistence in college.
- No heterogeneity in results is found based on the types of assignments offered in the class and the academic discipline of the class.
- The large sample size allows for precise estimates that rule out economically meaningful effects.
Class size is a first-order consideration in the study of education cost and effectiveness. Yet little is known about the effects of class size on student outcomes in online college classes, even though online courses have become commonplace in many institutions of higher education. We study a field experiment in which college students were quasi-randomly assigned to either regular sized classes or slightly larger classes. Regular classes had, on average, 31 students and treatment classes were, on average, ten percent larger. The experiment was conducted at DeVry University, one of the nation's largest for-profit postsecondary institutions, and included over 100,000 student course enrollments in nearly 4,000 classes across 111 different undergraduate and graduate courses. We examine class size effects on student success in the course and subsequent persistence in college. We find little evidence of effects on average or for a range of course types. Given the large sample, our estimates are precise, suggesting that small class size changes have little impact in online settings.