This article explains how to delete a quiz.
Click Content and select Quizzes.
To the right of the Quiz name in the table, click the Actions icon and select Delete. Confirm that you want to delete the quiz.
Confirm that you want to delete the quiz. Note that this deletion is permanent; the quiz cannot be recovered thereafter. All data associated with the quiz will also be permanently deleted.
If you have any course activities that used the quiz that has been deleted, you will need to select a new quiz or delete the activity.