Is it unreasonable to change the rules of a quiz/exam one week in advance?

I am that kind of student, so here's my perspective:

For one, I expect the rules to be clear when I sign up for a course. If you decide to change the rules after the start of the semester, it is not allowed to do so at the university I am attending unless you make sure that the change is better for the students. But even if a lecturer decides to add something like "You can hand in your exercises for bonus points" or "There will be a midterm for bonus points", it gets me on the wrong side - mostly because those "bonus" points are just as important as the non-bonus points and thus no different.

Similarly, you think that you are helping the students by forcing them to learn the material, but no matter how you try to force them, it just will not be helpful for every and all students in your class. For people like me, a huge amount of the motivation comes from the freedom of how to study: If I feel like a computer-written cheat-sheet helps me more, but I am forced to use a hand-written one, I will definitely come to you to complain.

Why?

• I like to do everything on the laptop, having every note always available, and if I have to do something by hand, I tend to scan it later. So handwritten just means more effort for me.

• I will never have such a good layout on my handwritten notes as on my digital notes. One reason being that I can change the content easily when I decide to move, remove, or reformulate something

• Typing is faster. If I already understand what I'm writing this is preferable. If I don't, I'd rather spend time on understanding first, and then write the notes - not thinking while writing and doing both only half as good.

What I would recommend you is to explain why you recommend handwritten notes, but still allow the students to decide. If you feel like it, you could state that their cheat-sheets need to be self-written - but neither this nor the handwriting is something that can easily be actually enforced. You won't be looking at every student's notes to check if they have one page too much, or if they plagiarized your slides and wikipedia for it, right? So why not just allow them to do it how they prefer - it's them who fail if they did it the wrong way. And they won't remember everything they have written by themselves either when they need to apply the knowledge in 3 years or so, so knowing where to look those informations up is also important.

To answer your questions:

Am I being unreasonable/unprofessional by changing the requirements for the quiz "cheat sheet" 10 days in advance?

I would say yes. Especially if the students have other midterms around the same time, preparing won't be done in just one week.

Is the student overreacting?

Possibly. Just by what you're saying, I would say not. But then again, I myself tend to overreact in such scenarios as well :)

Or are both of us in the wrong?

This student probably only considers his viewpoint, just like I only stated mine. Meanwhile, you only consider the students who need enforcements like self-written notes and who will never start with their cheat-sheets until a week before the midterm. I guess both are in the wrong, but it's probably a question of principle:

Do you want to put the self-disciplined students at a disadvantage because you want as many students as you manage to actually pass, or do you hand the responsibility for studying to the students?

Students preparing for finals are under a lot of stress. One way of coping with that stress is planning and visualization. A student may be boosting their confidence by thinking they have a really good cheat sheet already prepared for your test, and then you change the rules.

The notice seems unnecessarily short. Since the changed rule was a reaction to the mid-term, why not announce it immediately after the mid-term?

Handwriting-only is also an inherently unfortunate requirement for some students. I find it much easier to quickly locate information in a typeset printout than in anything handwritten. The more thought a student puts into organizing their cheat-sheet, the more they will lose by having to copy it out.

I am grateful for the input from the community. In the end, I decided that it was not fair to the students to change the “cheat sheet” policy with only a one-week notice.

Here is a summary of what I learned from the answers and comments written by the community.

• Timing is important
  If I had wanted to change the rules of the exam, I should have done so as early as possible. In this case, the most appropriate time would have been immediately following the first quiz.
• Is this battle worth fighting?
  Although I think that requiring handwritten “cheat sheets” only would be beneficial to most students, it is not a “must do” change right now, one-week before the quiz. Therefore, although I could use my "dictatorial" powers as a course leader to arbitrarily change the rules, I would face opposition from some students, and it is not wise to fight this battle. The right time to make this change is the next time that I teach the course.
• Should I create additional stress in students’ lives?
  Many students feel stressed around the end of the semester, when they are finishing assignments/projects and preparing for finals. Initially, I had thought that the handwritten only “cheat sheet” rule was a minor change, because I thought that it would take only one hour to copy your notes from a digital “cheat sheet” to a handwritten one. However, it was pointed out to me that to change the rules of the exam on short notice would create additional stress and frustration at an already difficult time.
• Is it fair to penalize students who work early?
  To change the rules 1-2 weeks before the exam would penalize the hard-working students who prepared early, while the student who work at the last minute would not be affected. Many of the students who prepared early will (rightfully) perceive this as being unfair towards them. They would feel as if the teacher were destroying the product of their hours of work.