I made a quiz with matching questions in 2.9. After the quiz was closed, I noticed that one of the answers was incorrect. So I edited that quiz question and did a quiz regrade for all 200 students in the course. Expecting one a one point difference in some of the scores, I was surprised to see that almost all the students had a difference of several points from the first quiz to the revised version. I reviewed the attempts of several of the students and found out that several of their choices were now showing "deleted choices". (see attached gif)
I realize it is probably too late to get those choices back, but what did I do wrong originally? I downloaded the results from the original quiz so I have the corrects scores, but I would like to know what I did wrong in order to not make the same mistake on future quizzes.
There is a general issue that you have to be very, very careful if you edit questions after they have been attempted. Some edits are safe, others are not.
- If you just change part of the text of a question, for example to correct a typo in one word, then this is fine.
- If you add or remove a bit of a question (for example a choice in a multiple choice question, or a subquestion in a matching question) then that is a disaster.
- (An unrelated example, but useful to know. With multiple choice and short-answer questions, it is safe to change the grade that each answer is worth.)
Because 1) is useful, we don't prevent editing after a question has been attempted. However, the fact we don't have a good way to stop people making the mistake 2) without realising the consequences is bad.
With matching questions, because of the way the student's response is stored in the database, it does not work to change what the right answer is. That is logged as MDL-5560, but there is no easy way to fix that, which is why it has gone unfixed for so long.
Thanks for the quick response. I will keep this in mind for next time. Keypoint: Don't make mistakes in the first place!