In this section, Professor Ketterle discusses the use of web-based problem sets in 8.421.
Transforming Questions
Traditionally, in 8.421, we have assigned standard problem sets that require students to submit weekly written solutions. In 2014, I collaborated with Professor Isaac Chuang to use the MITx platform to offer residential students interactive web-based problems. [Note to OCW users: The web-based problems are not currently available on the course site.] The MITx platform allowed students to ask for advice when they got stuck on a problem. When they submitted the wrong answer, they received that feedback immediately and could attempt the problem again.
Originally, I thought we would only be able to use the MITx platform for straightforward and highly structured problems. I thought that the more conceptual questions—those that require students to write longer derivations—would still need to be presented via the traditional paper format. In other words, I thought that students would answer perhaps 2/3 of the questions included in the course on the web, while submitting paper copies of their solutions for 1/3 of the questions. But Professor Chuang was so ingenious. He was able to transform every single question for the course into a question that students could answer interactively on the web.
Asking students to write the whole derivation in a way that other people can understand is an important educational experience.
—Wolfgang Ketterle
Finding a Balance
We’ve done this only once, so my experience is limited. However, what we learned was that despite some glitches and bugs, students wanted us to continue to offer web-based problems because they loved the immediate feedback 
. In the traditional format, students submit their solutions, and wait a week or so to receive their grade. At that point, they have forgotten about the question or they are already thinking about the next topic.
On the other hand, if I teach the course again, I want to carefully look through the problem sets. I think when we offer all the problems online, students miss out on writing longer derivations. Web-based problems prompt students to enter their responses, so of course, they must derive the answers first, but sometimes they might take a shortcut in the derivations or use sloppy handwriting, like they might when creating a draft of a solution. Asking students to write the whole derivation in a way that other people can understand is an important educational experience.
Also, it can be challenging to provide students with the kind of feedback they need to work through conceptual problems via a web-based interface. So, in the end, I think the web-based format may be more suitable for highly structured problems, simple exercises, and concept fluency. If I were to teach this course for residential students again, I would take a few of the higher level questions off the MITx platform and ask for paper submissions. However, for instructors teaching a course like this completely online, it’s extremely encouraging to know that even very complicated questions can be transformed into web-based problems.