Store user test results against their profile in Drupal Quiz Site
You can also create fields directly attached to the User entity just as you would to a content type.  It may make more sense to store the information for a specific user in fields attached to their identity directly. You can create views and panels to display the information however you want and provide hook functions in a custom module to do whatever specialized calculations you desire for presenting averages, grades etc.

I also noticed that you have used the Profile tag which relates to a module that has been deprecated for D7.  If you have the module enabled, I recommend not using it for any future site since it will very likely not be maintained in D8.