You can grant access to an individual student, several students, or the entire class to have extra attempts on a quiz. If you have set a time limit on your quiz, you can allow for extra time on each attempt for students.
Giving a student an attempts and/or extra time on a Quiz:
1. In the "Quizzes" menu, click on the Quiz the student needs an extra attempt or extend time on
2. Click "Moderate This Quiz"
3. Find the student's name in the list and click on the pencil icon to the right of their name.
4. In the menu that appears, you can set the following options (see screenshot below):
(A) The number of extra attempts
(B) Extra time to be added to the set time limit on each attempt
(C) Manually unlock the quiz for the next attempt: You must select this if the student is taking the quiz AFTER the set due date or availability date of the quiz has passed. If you don't select this, the quiz will remain locked and the student will not be able to access the quiz.
5. Click "Save" to save the set options.
See the Support Article below for more information - http://guides.instructure.com/s/2204/m/4152/l/50753-once-i-publish-my-quiz-how-can-i-give-my-students-extra-time-or-extra-attempts