Membership of Mensa is open to persons who have attained a score within the upper two percent of the general population on an approved intelligence test that has been properly administered and supervised.e offer 2 ways to practise: 1  Our online Mensa Workout is an intelligence quiz in which you have half an hour to answer 30 questions. 2  In some countries, a pre-test is available which you can take in the privacy of your home.