Go to Gradable Activities
Select Quizzes
Select the chevron next to the Quiz name
Choose Grade
Click on the Attempts tab
Click on the Show Search Options (next to the search box)
From the Restrict to drop down menu, choose Users with attempts in progress
Select the Search icon next to the search field and scroll down the page to view results
Next to the attempt click the Enter Quiz as User ("people" icon)
Confirm on the pop up, choose Yes