Deviation IQ
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Deviation IQ is the modern way of computing IQ as 100 + 15 × z, comparing you against same-age peers rather than using a mental-age formula. It replaced the older ratio IQ and is what every major test uses today.
IQ Glossary & Terms
IQ (Intelligence Quotient)
Ratio IQ
General Intelligence (g)
Fluid Intelligence (Gf)
Crystallized Intelligence (Gc)
Percentile
Standard Deviation (SD)
Normal Distribution (Bell Curve)
📅 Last updated: 2026-06-18 · ✔ Reviewed by the All-Lifes editorial team ·
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📚 Sources & references
IQ classification — Wikipedia
Mensa International — What is IQ?
APA Dictionary of Psychology — Intelligence
Raven's Progressive Matrices — Wikipedia
Cattell–Horn–Carroll theory — Wikipedia
Flynn effect — Wikipedia
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IQ Glossary & Terms