To better understand the spacing effect in education, it's important to research what type of learning decisions students make when learning is self-regulated (as opposed to directed spacing in lab settings). One study used student data collected from a MOOC to examine if to examine various self-regulated spacing decisions and how they relate to student ability and learning outcomes. Spacing was defined as the number of sessions a student spent studying the unit that was covered by the quiz. Pretest grades (used to measure prior knowledge) and time spent in unit were used as predictor variables of performance. Data was analyzed from quizzes on 11 different units so that spacing effects could be examined within the same student.