IQ reference charts are tables suggested by IQ test

Intelligence quotient

An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...

 publishers to designate IQ score ranges as various categories. As reference charts, they are not to be taken as absolute or precise. All IQ tests show variance in scores even for the same test-taker retested on the same test, and also variance in scores among IQ tests from different publishers. Category labels for IQ score ranges are specific to each brand of test and are arbitrary.

Terman classification

Lewis Terman

Lewis Terman

Lewis Madison Terman was an American psychologist, noted as a pioneer in educational psychology in the early 20th century at the Stanford University School of Education. He is best known as the inventor of the Stanford-Binet IQ test...

, developer of the Stanford-Binet intelligence test, chose the category ranges for score levels on that test using a standard deviation

Standard deviation

Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...

 of 16.

Terman's Stanford-Binet Fourth Revision classification

IQ Range ("Deviation IQ")	Intelligence Classification
152 and over	Genius and near genius
148 - 151	Very superior intelligence
132 - 148	Superior intelligence
116 - 132	Above average intelligence
84 - 116	Normal or average intelligence
68 - 84	Dullness
52 - 68	Borderline deficiency
Below 52	Mental Deficiency

Wechsler classification

The Wechsler Adult Intelligence Scale

Wechsler Adult Intelligence Scale

The Wechsler Adult Intelligence Scale intelligence quotient tests are the primary clinical instruments used to measure adult and adolescent intelligence. The original WAIS was published in February 1955 by David Wechsler, as a revision of the Wechsler-Bellevue Intelligence Scale...

 uses the following category labels, the scores are scaled with a standard deviation

Standard deviation

Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...

 of 15.

Wechsler's classification

IQ Range ("Deviation IQ")	Intelligence Classification
>= 130	Very superior
120 - 130	Superior
110 - 120	Bright normal
90 - 110	Normal
80 - 90	Dull normal
70 - 79	Borderline
50-55 to ~70	Mild Mental Retardation (MR)
35-40 to 50-55	Moderate MR
20-25 to 35-40	Severe MR
<= 20-25	Profound MR

See also

• Intelligence quotient
  Intelligence quotient
  An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean score within an age group is set to 100 and the standard deviation to 15...
  
  
• Level of measurement: Ordinal scale
• Intellectual giftedness
  Intellectual giftedness
  Intellectual giftedness is an intellectual ability significantly higher than average. It is different from a skill, in that skills are learned or acquired behaviors...
  
  
• Mental retardation
  Mental retardation
  Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
  
  
• Stanford-Binet Intelligence Scales
• Wechsler Adult Intelligence Scale
  Wechsler Adult Intelligence Scale
  The Wechsler Adult Intelligence Scale intelligence quotient tests are the primary clinical instruments used to measure adult and adolescent intelligence. The original WAIS was published in February 1955 by David Wechsler, as a revision of the Wechsler-Bellevue Intelligence Scale...