IQ classification

An example of a general IQ reference chart

I.Q. Range (15SD)	Intelligence Classification
25 - 40	Severe mental disability
40 - 55	Moderate mental disability
55 - 70	Mild mental disability
70 - 85	Borderline mental disability
85 - 114	Average
115 - 130	Above average
130 - 145	Moderately gifted
145 - 160	Highly gifted
160 - 175	Exceptionally gifted
Over 175	Profoundly gifted

IQ reference charts are tables suggested by psychologists to divide intelligence ranges into various categories. As reference charts, they are not to be taken as absolute or very precise. The reason for this is the lack of a uniform definition of intelligence and the current inability to wholly quantify it in a scientific manner. To get a "true" IQ score, multiple IQ tests must be taken since professionally administered IQ tests are only roughly 96% reliable. The average of multiple tests, usually at least three, is considered that person's "true" IQ score. However, these tests must be taken within a relatively short period of time, normally under one year for three or more tests.

Terman Classification

Lewis Terman, inventor of the Stanford-Binet intelligence test, later devised a classification based on gradations of 16 (Standard Deviation):

Terman's classification

I.Q. Range (16SD)	Intelligence Classification
164 and over	Genius or near genius
148 - 164	Very superior intelligence
132 - 148	Superior intelligence
113 - 132	Above average intelligence
84 - 113	Normal or average intelligence
68 - 84	Dullness
52 - 68	Borderline deficiency
Below 52	Definite feeble-mindedness

Wechsler Classification

David Wechsler, inventor of the Wechsler Adult Intelligence Scale, based his own classification on the probable error of IQ rather than the range.

Wechsler's classification

I.Q. Range (15SD)	Intelligence Classification	Percent Included
128 and over	Very superior	2.2
120 - 127	Superior	6.7
111 - 119	Bright normal	16.1
91 - 110	Average	50
80 - 90	Dull normal	16.1
66 - 79	Borderline	6.7
65 and below	Defective	2.2

Mental deficiency

Note: These terms, once used to classify levels of mental deficiency, are now considered terms of abuse:

Mental deficiency

I.Q. Range	Intelligence Classification
70 - 80	Borderline deficiency
50 - 69	Moron
20 - 49	Imbecile
Below 20	Idiot

Now mental retardation is classified differently:

Mental retardation

I.Q. Range	Intelligence Classification
50 - 69	Mild (educable)
35 - 49	Moderate (trainable)
20 - 34	Severe
Below 20	Profound

See also

• Intelligence quotient
• General intelligence factor