As Emma says, the changed question will show up immediately to all users.
Note, you must be very, very careful doing this. Some changes are safe, for example:
- Changing the wording of the question/feedback, for example to correct a spelling mistake, or make it clearer.
- Changing which choice in a mulitple choice question gets awarded 100%
- Changing the the rules for how a shortanswer or numerical question is graded.
- Changing the number of marks each question is worth.
Some changes will break things badly, for example
- Adding or deleting a choice from a multiple choice question.
- Changing which answer in a matching question goes with which subquestion.
- Editing the subquestions of a Cloze question.
Do not do these things.
If you have time, try things out first on a separate quiz that you created just for testing to see if you proposed change is safe.
For some of these changes to take full effect, you will need to go to Quiz adminsitration -> Results -> Grades, and regrade the quiz. However, it is safest to wait, and only do that after the quiz has closed.