Number of students enrolled on the last day of Stat 2.1X: 52,661
Active in the last week: 10,609
Earned certificates: 8,181
If you define "completion" as "earned certificate," the completion rate is 15.5%.
For comparison, here are data from a blog by Katy Jordan. She has some beautifully presented data complete with sources; it's a pleasure to read what she writes. Her data points, provided in February 2013, consist of 27 MOOCs, mostly from Coursera. Here's a stem-and-leaf plot of the completion rates in her table.
Stat 2.1X students will know how to read this once I've told them that the first line reads 0.7%. For others, here is an expanded version of the first three lines; you can take it from there. The entries are percents.
2.3 2.3 2.6 2.7
and so on
COMPLETION RATES OF 27 MOOCS [source: February 2013 data summary by Katy Jordan]
0 | 7
1 | 7
2 | 3367
3 | 25
4 | 5678
5 | 24
6 | 056
7 | 036
10 | 118
12 | 56
13 | 8
19 | 2
The median is 5.4 by the conventional "half-way point of the data" definition. 5% is often quoted as a "typical" MOOC completion rate.
Coursera's Scala course is at 19.2. It was taught by Martin Odersky who designed Scala.
We're not at 19.2, but even so, 15.5% is exceptionally high on the scale of MOOC completion rates.
I've been thinking about what it means to "complete" a course like Stat 2.1X. "Earned certificate" is a measure that sticks with the usual conventions of exams, grades, and so on. But it's possible for a student to go through all the lectures and try the exercises without regard to due dates and grades, as long as the course materials are available. That's a form of completion too, and a perfectly reasonable one for students who want to learn the subject but don't need or want a certificate.
They're hard to keep track of. But I'm willing to bet they're a big group.
To them - indeed, to all those who made a determined effort in Stat 2.1X, especially those who got the certificate: well done, and thank you for exploring this new world with me.