We also examined student persistence through the course. Unlike courses that begin and end on set dates, students could join JusticeX at any point. Moreover, there were no incremental due dates throughout the course—only a final due date—so late registrants could complete all of the work of the course, even those who registered on the final day of the course. The official course launch was March 2, 2013; the first content was released on March 12; the final exam was made available on May 28; and all assignments were due by August 2. Some students engaged in the course at the pace that the content was released, completing two lecture units every week from March through May. Students could also sign up for Justice in July, and, to borrow a phrase from contemporary television viewing habits, “binge-watch” the course and complete all assignments over a weekend.
Therefore, to examine student persistence, we focused more on each student’s relative timescale—the time from their enrollment or the course content launch, whichever was later—rather than on the absolute time in the course.
In Figure 14, we show an average hazard function derived by empirically calculating the hazard proportions of each weekly registration cohort and then averaging across the hazard proportion in each relative week. Thus we evaluated the questions: “What proportion of students stop participating during their first week? Their second week? (and so on…).” We can then infer the proportion of students who would remain from week to week in each cohort. This is an “implied survivor function” calculated directly from the average hazard function.
Figure 14. Hazard function comprised of the average of all registration cohort hazard functions plotted on relative course week (where week 0 is the course launch or initial registration week, whichever is later) and truncated at week 21 when the final exam was due. Implied survival function is calculated directly from the average hazard function.
The key insight from this figure is that, within each weekly registration cohort, students are very likely to cease activity during the week that they register and right afterwards. After that, however, hazard proportions drop to below .2 and level out below .1 after the fifth week. Colloquially, if a student gets hooked on a course within the first two weeks—regardless of when s/he starts—s/he is likely to stay, or at least the risk of dropping out in any subsequent week is constant.
This survival model gives some sense of how students persist throughout the whole course, examining the span of time from first action to last action. However, a student could log in only twice, on the first day and the last day, and be counted as “surviving” through the length of the course. This motivates an alternative metric that counts how many discrete days students view course material. Among all registrants, we find that median number of days of activity is two, and 75% of registrants have seven or fewer days of activity.
For a more granular view, therefore, in Figure 15 we examine the daily activity of those who have viewed over half the course (those who “explored”) as well as certificate earners. We see that among these active students, most had between 10 and 40 days of activity, with a long tail of students who spent over 100 days within the period from March 3 to our date of data collection on September 8.
Figure 15. Days with activity, the number of discrete days (demarked in UTC time) during the observational period where participants had at least one action, for explorers and certificate earners (n=8,415).
These contrasting figures illustrate the diversity of ways of participating substantially in the Justice course. Most people took an action one or two days a week over the 26 week period that we examined; however, some students participated over the course of only a few days, and still others engaged much more frequently.