If we know what we are better prepared, have fewer difficulties in the struggle for life. We would be happier and more productive making each one what better knows or can do. The common denominator to distinguish for what is good, is intelligence. Intelligence tests are the key to determine the vocational and intellectual aptitude of persons. Alfred Binet with Theodore Simon developed the test to measure the intelligence of retarded children, based on the observations that as children grow and become older, it also increases your mental capacity and some may have superior performance to their grade level and chronological age while others do not. In their studies, a six year old boy could surrender as well as one of eight, while another six could pay as little as one of four. In 1911 was introduced the concept of mental age (MA) as opposed to chronological age (EC). Child from 6 years which surrendered as well as 8, you were assigned a mental age of 8, while that of 6 that surrendered just as the aged 4, was assigned a mental age of 4.
Although the distance between mental age and chronological enlarges as the child matures, the difference between both ages is kept constant. This constant is named it the intellectual quotient (CI). Scientifically, the CI is defined as 100 times the Mental age divided about the chronological age. (CI = 100 MS/EC) At age 16, mental age as well as the height, cease to increase. The average IQ is by definition 100. For under 120 CI, IQ is the best indicator to future of the socio-economic status of the people. The CI is better than the education or experience to predict on-the-job performance. Adults in the lowest 5% of the CI (less than 75) are very difficult to train and are not competent to any work on the basis of their ability.