An individual is typically considered mentally retarded if their IQ falls below which value?

• A. 100
• B. 85
• C. 75
• D. 70

Answer: (D)

IQ tests are scaled so the average is 100 with a standard deviation of about 15. An IQ score below 70 falls more than two standard deviations below the mean, indicating a level of cognitive functioning that is significantly impaired compared to peers. This level has long been used as the cutoff for labeling intellectual disability, recognizing that diagnosis also depends on deficits in adaptive functioning and onset during the developmental period. Therefore, the value to remember is 70. Scores like 75, 85, or 100 do not meet that threshold, as they indicate milder impairment or typical functioning.