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Online discussion forums in a MOOC setting allow students to become aware of other students enrolled in the course. However, what is (usually) visible in the forums is the output of ``active'' students who engage in asking and answering questions. In addition to such active participants, there is (as always in online communities) a large group of ``passive'' users (so-called lurkers), who might find the forum useful to their learning, and read it regularly, despite remaining ``invisible''. Our analysis of a large MOOC online forum shows that for every active participant in the forum there are two passive ones. 30% of active participants complete the course, compared to only 6.6% of the passive participants. Vice-versa, 67% of students who complete the course are also active in the forum. However, ``invisible activity'' (e.g. reading or searching the forum) is something that both groups practice equally and more frequently, while only 3.3% of forum actions are visible.
Mustafaraj et al. (Mon,) studied this question.