Confidence Scores for Exam Questions (nomagicpill.substack.com)

I seem to remember some medical related multiple choice tests in the UK use a mechanism of +1 for correct , 0 for unanswered , -1 for incorrect.

It would make more sense to just use IRT for grading the responses than trying to add more complexity to the answers themselves.

Moodle has had certainty based marking for at least 15 years.

https://docs.moodle.org/502/en/Using_certainty-based_marking