Create a new quiz. Add a matching question A -> a, B -> b, C -> c, D -> d Add a second matching question 1 -> i, 2 -> ii, 3 -> iii, 4 -> iv Attempt the quiz as a student and get both questions right. Attempt the quiz as a second student and answer A -> c, B -> b, C -> a, D -> d for the first question, and any answer you like for the second question. As teacher/admin, go to Results -> statistics in the Quiz administration. Click on the name of the matching question, and check the Response analysis table contains the right counts. Go to the Edit quiz page. Edit the question, and delete the subquestion C -> c. (Note, this is a really bad thing to do to a question in a quiz that has been attempted. Never do this for real.) Edit the second question and add an extra choice 5 -> v. Go back to quiz statistics. Click the recalculate now button. Check that the response analysis shows some numbers, however meaningless, without any fatal errors or warnings or notices.