I'm not sure. 'Drugs and the Brain' was the first one I tried - before I had been put off by the forced scheduling, but this makes sense if they're depending on peer grading. The technical aspects are better than 'Marginal Revolution University', but I can't compare to many others. One thing I liked about the CMU OLI course was that it had a lot of questions and quizzes, which is something 'Data Analysis' is currently falling down on the job a bit anent.