IQ is measured using standardized tests designed to assess various cognitive abilities. Commonly used IQ tests include the Wechsler Adult Intelligence Scale (WAIS), Stanford-Binet Intelligence Scales, and Raven's Progressive Matrices. These tests evaluate skills such as reasoning, problem-solving, memory, and verbal comprehension. The IQ score is often calculated by comparing a person's performance to a normative sample and scoring on a scale with an average of 100 and a standard deviation of 15. The classic formula for IQ is IQ=mental agechronological age×100\text{IQ}=\frac{\text{mental age}}{\text{chronological age}}\times 100IQ=chronological agemental age×100, though modern tests use norm-referenced scoring.
IQ tests can be administered by licensed psychologists in controlled environments for accurate results, or there are various online tests available though their reliability varies. Well-known tests like the WAIS and Stanford- Binet can take from about 30 minutes to over an hour to complete and provide a comprehensive assessment of intellectual capabilities.
