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.
Yeah, OP should take this as a opportunity to work on assignment design and course policies for the next time. There have been plenty of times where students did something that I viewed or suspected as dishonest but didn’t report them for it because I hadn’t designed my assignments well or didn’t have a clear policy against it.