I think of the number of times that a student has come to my office to question his or her grade. I would ask them: "Can you read to me what you wrote? Just read it aloud to me." They would start reading, then stop and say: "Well, I didn't write xxx, but of course that was what I had in mind". They would continue, then stop in some embarrassment at the lameness of their style. The lack of precision in their writing would be painfully obvious, and sometimes they couldn't help but laugh at themselves. I wouldn't need to explain why they didn't get full credit: once they read aloud, the reasons became obvious.

A webcast might be the answer!

I find this to be a great idea! I think this idea could strike the right balance between rigor and brevity for homework assignments: sometimes there are things I can 99%-rigorously explain in 30 seconds with some gesturing on a whiteboard, whereas to write it up 100%-rigorously in LaTeX would take 30 minutes -- eating up valuable time for both students and graders.

ReplyDeleteAt UIUC, we had (still have?) something similar when I was a TA. For each assignment in an undergrad theory class (automata theory, algorithms, ...) half the students would submit the usual written solutions, and half would have to present their work to a TA on a whiteboard (more low-tech than a video).

ReplyDeleteThe disadvantage is that it takes a lot longer to grade than written solutions. Listening to a 2-3 minute explanation can take longer than scanning down a page to verify whether a proof is correct. And we found that to be most effective, we had to give them nearly 10 minutes for a problem.

That said, I loved it. It was more effective feedback for the students, who immediately found out why their "proofs" were incorrect. With written solutions, students often don't even read the grader's comments, and when they do, it's been over a week since they last thought about the homework, so it isn't fresh in their minds. One can also show them counterexamples to their claims, which allows them to see gaps in their proofs; many of them even come up with a fix during the presentation. One can really observe an improvement in proof construction skills over the course of the semester.