by Jamie Pratt.
What you want to do might be best done as a quiz report. You can write a new plug in to define a quiz report. And quiz reports can set up tables for their own purposes in the Moodle db.
But there would be advantages to making a special question type too. Probably you could extend the existing multiple choice question type and add bits to the question editing form to specify a category for each answer. If you make a special question type then you could back up and restore and export import this information too, which you would not be able to do from within a quiz report plug in.
Tell us more about what you mean by 'kind of mistake'?