How to Create a Moodle Quiz: Step-by-Step Guide
3. Setting #2: Grade. Set a Passing Grade (Optional)
With the default settings, students have an unlimited number of attempts to answer the same question. As a result, a quiz can be passed by a random choice method: they make a mistake and immediately change the answer, and so on until they pass. If you prefer learners not to play guessing games, limit the number of attempts and set a passing score.

Passing grade
This is the minimum score required to pass a quiz. The pass grades are highlighted in green, and fail grades in red.
Number of attempts
If this is a final exam, you can give just one attempt, and unlimited for a practice quiz.
Grading method
If this is a practice, students get to keep the highest grade they have achieved.