Mensa is the largest and oldest high IQ society in the world. It is a non-profit organization open to people who score at the 98th percentile or higher on a standardized, supervised IQ or other approved intelligence test. Mensa is formally composed of national groups and the umbrella organization Mensa International, with a registered office in Caythorpe, Lincolnshire, England. Mensa's requirement for membership is a score at or above the 98th percentile on certain standardised IQ or other approved intelligence tests, such as the Stanford-Binet Intelligence Scales. The minimum accepted score on the Stanford-Binet is 132, while for the Cattell it is 148. Most IQ tests are designed to yield a mean score of 100 with a standard deviation of 15; the 98th-percentile score under these conditions is 131. Full, Supervised Mensa IQ Test sessions take around two and a half hours and are administered under strictly controlled conditions . We then mark your IQ test papers and your results returned to you in confidence for a one off fee of £24.95.