Intelligence is an abstract concept. It is difficult to measure intelligence level and express it in numbers. However, the term Intelligence Quotient is used for the purpose. This term became popular about a hundred years ago in 1916 when a Stanford University psychologist named Lewis Terman invented a formula to numerically measure the amount of intelligence in a human being. The formula was revised in 1937, then in 1960, and the last time in 1972 there were a few changes done to the formula. The formula used today to measure IQ is as follows:
IQ = Mental Age ÷ Physical Age x 100
In the formula, physical age is one’s age from the date of birth, but mental age is a completely different matter. To explain with an example, if a 10-year-old correctly answers questions which can normally only be answered by a 13-year-old, then even though his physical age is 10 years, his mental age is considered to be 13 years. Thus, according to the formula, his IQ would be 13 ÷ 10 x 100 = 130. On the other hand, if a 10-year-old answers questions which can normally only be answered by a 10-year-old (and he can’t answer tougher questions), then his IQ would be 10 ÷ 10 x 100 = 100. It means his mental and physical age are the same.
A person with IQ of 100 can not be said to have a sharp mind, because the IQ figure of 100 is normal. It also means that majority of the people the in world have an IQ of 100. Refer above the distribution of Intelligence Quotient.
To tell the truth, human intelligence level can not be determined mathematically with accuracy, intelligence being an abstract concept. Therefore, the formula for measuring IQ is not very reliable. According to this formula a woman named Marilyn vos Savant has IQ of 228, whereas Albert Einstein’s IQ is said to be 160.