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IQ Classifications

AssessmentPsychology.com > Assessment > IQ Scores > IQ Classification

 

IQ Classifications in Educational Use

Wechsler, David. Wechsler Adult Intelligence Scale-Third edition
Psychological Corporation, 1997

Classification

IQ Score Percent Included
    Theoretical Normal Curve Actual Sample
Very Superior 130 and above 2.2 2.1
Superior 120-129 6.7 8.3
High Average* 110-119 16.1 16.1
Average 90-109 50.0 50.3
Low Average* 80-89 16.1 14.8
Borderline 70-79 6.7 6.5
Extremely Low*  ** 69 and below 2.2 1.9

*The terms High Average, Low Average and Extremely Low correspond to the terms Bright Normal, Dull Normal and Mental Defective, respectively, used in the 1955 WAIS manual.

**The term Extremely Low is used in place of the terms Mentally Retarded, used in the WAIS-R, and Intellectually Deficient, used in the WISC-III to avoid the implication that a very low IQ score is sufficient evidence by itself for the classification of "mental retardation" or "intellectually deficient."
 

IQ Classifications in Psychiatric Use

Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)
American Psychiatric Association, 1994

V62.89 Borderline Intellectual Functioning IQ 71-84
317 Mild Mental Retardation IQ 50-55 to approximately 70
318.0 Moderate Retardation IQ 35-40 to 50-55
318.1 Severe Mental Retardation IQ 20-25 to 35-40
318.2 Profound Mental Retardation IQ below 20 or 25

The terms Educable Mentally Retarded and Trainable Mentally Retarded used in special education are roughly equivalent to DSM classifications for mild and moderate mental retardation, respectively.  The DSM diagnostic criteria further require an assessment and determination of impairment in adaptive functioning in order to make a diagnosis of mental retardation.
 

IQ Classifications No Longer in Use

Terman, Lewis M. The Measurement of Intelligence. Houghton Mifflin Company, 1916
An explanation of and complete guide for the use of the Stanford Revision
and extension of the Binet-Simon Intelligence Scale
140 and over Genius or near genius
120-140 Very superior intelligence
110-120 Superior intelligence
90-110 Normal or average intelligence
80-90 Dullness
70-80 Borderline deficiency
Below 70 Definite feeble-mindedness

Mental deficiency used to be divided into the following sub-classifications, but these labels began to be abused by the public and are now largely obsolete: Borderline Deficiency (IQ 70-80), Moron (IQ 50-69), Imbecile (IQ 20-49) and Idiot (below 20). Mental deficiency is now generally called mental retardation.


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