The documentation below demonstrates the process involved in updating scores on a quiz. This can be used when you have either incorrectly marked an answer or want to give credit to an answer that previously received none.
*Note: The screenshots/steps below show this process when regrading a true or false question; however, other quiz question types follow the same type of process.
Log into your course and from the Assessments drop-down menu click Quizzes.
From the drop-down menu next to the quiz click Grade.
Select the Questions tab.
To regrade all attempts select Update All Attempts. Then select the question you want to rescore.
Scroll down to the Grade heading and re-score accordingly by selecting either Give to all attempts __ points or Give to attempts with answer. Click Save.
The question has now been successfully rescored.