Virtual Classrooms: How Online College Courses Affect Student Success
使用工具变量方法，研究发现在线课程相比线下课程降低了学生的成绩和学业进展，学生更可能退学，该效应适用于同时有在线和线下选择的学生。
Online college courses are a rapidly expanding feature of higher education, yet little research identifies their effects relative to traditional in-person classes. Using an instrumental variables approach, we find that taking a course online, instead of in-person, reduces student success and progress in college. Grades are lower both for the course taken online and in future courses. Students are less likely to remain enrolled at the university. These estimates are local average treatment effects for students with access to both online and in-person options; for other students, online classes may be the only option for accessing college-level courses.