I gave my students a take home exam over spring break. (This is normal where I teach) One of the questions was particulary difficult. It came down to a factor of three in the solution. That factor inexplicably appeared with no justification on many of their exams. I intend to have the students I suspect of cheating come to my office to solve the problem on the board. What would you do?
Edit: I gave them the Tuesday before spring break until the Thursday after. I didn’t want it to be right before or right after.
When I say normal I mean giving take home exams.
I think this is a really good, well-measured answer. The only thing keeping it from being perfect is your bit defending the idea that a take-home exam is not open-book. I think the reply from @livus@kbin.social is excellent here. Any assessment needs to be tailored to the goals of the assessment. A take-home exam is one where the teacher has no ability to restrict a student’s access to their books or the Internet. So they shouldn’t even try. The questions should be tailored to test their understanding of the underlying principles, or even better, should encourage their ability to do research.
Sure, just posting the entire question on Stack Exchange and blindly repeating the answer you get there is cheating. But you need to actually think about the format of the assessment and play to its strengths, not try to ignore them. If you want a closed book exam, have a traditional exam with an invigilator.