David Wechsler: developed another set of age-based intelligence tests: the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) for preschool children, the Wechsler Intelligence Scale for Children (WISC) for ages 6 to 16, and the Wechsler Adult Intelligence Scale (WAIS ) for older adolescents and adults.
Intellectual disability:Â Test takers who fall two deviations below the mean have a score of 70
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