This EAGER project seeks to study a Massive Open Online Course (MOOC) offered by HarvardX, an experiment created in response to a need by Harvard faculty for a central resource to help them push the boundaries of learning through re-imagined teaching and to take advantage of new possibilities for educational research in the online era. The topic of the study is "Introduction to Computer Science", a course with the largest initial enrollment of all of Harvard's MOOCs (150,349), as well as the second largest enrollment of all of Harvard's traditionally taught courses (714). Two versions of this course, CS50x and CS50, share many features (lectures, problem sets, exams, and projects), but differ in grading, student feedback, and classroom interactivity. Unlike the traditional course which has a 99.6% completion rate, CS50x awards completion certificates to only 6.3% of those who enroll. This presents an opportunity to study high attrition rates in MOOCS, a problem that plagues online courses nationwide. Little is known about why students do not finish MOOCs. Are there disparities in completion rates by gender, minorities underrepresented in STEM, age of students, language fluency? The project gathers empirical evidence in the CS50x MOOC to create a profile of the enrolled students and to determine which factors in their background, in their prior experience with computing, and in their learning behaviors during the course, predict successful completion of the course. Statistical survival analysis will be used to model the risk of dropping out. The broader impact of the project is that, by characterizing factors that positively and negatively influence students' success in MOOCs, it will allow for more informed, and hence more potentially effective, pedagogical and institutional policies aimed at increasing student success and broadening participation.