Understanding & Interpreting IQ
(Intelligence Quotient)

Last updated:
01 Oct 2005

Understanding & Interpreting IQ


Summary: Understanding IQ

To understand IQ (Intelligence Quotient), you should first have an idea about what intelligence is - read various definitions.

IQ scores reflect general capacity for performing intellectual tasks, such as solving verbal and mathematical problems.

The average IQ score is 100.  The standard deviation of IQ scores is 15.  So, this means:

  • 50% of people have IQ scores between 90 and 110
  • 2.5% of people are very superior in intelligence (over 130)
  • 2.5% of people are mentally deficient / impaired / retarded (under 70)
  • 0.5% of people are near genius or genius (over 140)