Your initial course quiz settings can be overridden to set special quiz access for individuals or for groups of students. For example, an individual student can be given unlimited time to take an otherwise timed quiz, such as when a student has a Disability Services accommodation. Use the Unlimited Test Time User role for that student. This will give them an extension in all your Quiz activities. A quiz can also be re-opened for a student who missed it. Do this with the User Overrides link. Finally, quiz settings can be overridden for groups of students. For example, you might want a quiz to become available to different groups of your students at different times. Do this using the Group Overrides link.