After a quiz has been graded you have the option to view User and Question Statistics for that quiz.
To access quiz statistics click the drop down next to the quiz name and select Statistics.
User Stats contain performance data by user, first name, last name, the user’s score as a percentage, the class average and score distribution.
Question Stats contain data about the average score on questions by percentage.
Question Details contain detailed information about each question in the quiz, including a list of all of the answers provided for each quiz attempt, how many users chose each possible answer, the total number of responses, and the average score on the question. Question Details reports can help you evaluate trends in answers and look for questions that were unclear or difficult for a number of users.