Online versions of statistics courses have been taught for some time, but more information is needed on the effectiveness of using different approaches to teaching statistics online. The present paper describes a mastery-based approach to teaching an online introductory statistics course and presents data suggesting that the course is effective. Based on the evidences, the study suggests that faculty who are considering developing a similar online course should be aware that the instructor must invest a large amount of time to develop course materials and to provide prompt feedback to students. (Contains 5 tables.)