IQ Test

What is IQ?
Many who use the word IQ do not know the exact meaning of it. IQ stands for intelligence quotient. Actually it is a quotient though written as an integer. The early intelligent tests were based on the practice of comparing the mental abilities of children with the abilities of children of the same age and other children. A concept of mental age was used for defining the intelligence quotient. If a child can do what the children of 12 years can do and nothing more than that, the mental age of the child is considered as 12 years. When the mental age is divided by the chronological age of the child the result expressed as a percentage is the intelligence quotient.

IQ tests and Defining IQ
Mental age method gives an actual quotient and was first used by William Stern a psychologist from Germany. He used the quotient of mental age and the chronological age of the child taking the test multiplied by 100 as an indicator of the intelligence of the child. He named this quotient as Intelligence Quotient. This method had some shortcomings. The most serious one was that the method did not work well for the adults. Earliest version of Stanford-Binet IQ test scale also used mental age method. Although modern IQ tests do not use mental age or calculate any quotient the word IQ is still used for the indicator of intelligence.

Modern IQ Tests
Most of the modern IQ tests use the method first introduced by Wechsler. In this method it is assumed that the intelligence of a population conforms to a normal distribution. When constructing a new test, the test is given to a representative sample from the population. The median of the sample is defined as 100 IQ points. The results are used as the standard. The normal distribution curve for the intelligence is assumed to have a standard deviation of 15. When a person takes the IQ test his/her score is compared with the standardization curve and the IQ of the people with same score is assigned to the subject.