If I edit a test that I’ve already given, will it affect the student results?
If you change the number of questions on a test, the percent of questions each student had correct will be adjusted.
If you edit a question, such as updating to a better image, it will not change the students data.
However, if you change what the question is asking, that data no longer reflects what the student knows. So although you are able to make a change like this, it is not recommended. Especially if others are using the test you created.