To maximise multiple choice test scores under formula scoring, students must be able to monitor their knowledge level, reporting correct answers and withholding incorrect ones. Importantly though, neither metacognitive monitoring nor optimal criterion setting has received much attention in the formula-scoring literature. The present research examined the role that both these parameters have on obtained test score. Students wrote three exams under formula-scoring rules, and from these data, we created bias profiles using methodology developed by Higham ( 2007), which allowed us to estimate the optimal number of questions that students needed to answer to maximise their scores. The results indicated that higher scoring students monitored their knowledge best, but that all students tended to guess too often, lowering their test scores. This conservatism maintained despite feedback from previous tests. The results also showed that monitoring is a stable participant skill that generalises across tests.