1. Select Users & Security, Roles.
  2. Create a Survey Editing role.
  3. Select Users & Security, Users.
  4. Edit the users and add this role to them.
  5. On the page with the survey select Page Properties.
  6. On the Targeting & Security tab grant this role edit rights.
  7. Edit the survey part.
  8. On the Targeting & Security tab grant this role edit rights.