Thanks Tim. I wanted to use Moodle Adminer to download a bulk CSV file with student responses, rather than look at quiz attempts one by one, in order to take the responses into Excel to do some matching. I found the responses to one of the regraded questions in mdl_question_attempts, imported them in Excel, and used the Exact function to identify the mismatches, so I can share with the instructor what some of the subtle mismatches were.
I think the take-home message for the instructor is that there are so many subtle 'mismatches' possible that she will need to be very intentional and complete about what acceptable answers she includes when writing the questions.
Thanks again everyone. k