Intelligence quotient, more commonly known as IQ was developed by William Stern. He developed the concept based on tests such as the Stanford-Binet. To calculate an individuals IQ score you take their mental age divided by their chronological age and multiply it by 100. Although the IQ was a good idea it didn't work as well for adults as it did for children. The IQ scores represent the test takers performance relative to the average performance of others the same age. Usually the standard deviation of scores is 15, with the mean score being 100; 100 being a perfect IQ scores. this means that you have the same mental age as your do chronological age.