With Certainty Based Marking (CBM) getting every question correct with C=1 (low certainty) gives a grade of 100%. Grades may be as high as 300% if every question is correct with C=3 (high certainty). Misconceptions (confident wrong responses) lower grades much more than wrong responses that are acknowledged to be uncertain. This may even lead to negative overall grades.

**Accuracy** is the % correct ignoring certainty but weighted for the maximum mark of each question. Successfully distinguishing more and less reliable responses gives a better grade than selecting the same certainty for each question. This is reflected in the **CBM Bonus**. **Accuracy** + **CBM Bonus** is a better measure of knowledge than **Accuracy**. Misconceptions can lead to a negative bonus, a warning to look carefully at what is and is not known.