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Most people think an IQ score is a grade — like a 95 in maths. It isn't. How IQ is measured has nothing to do with how many questions you got right. It's a statistical position on a curve, comparing your performance against thousands of other people in your age group.
Every modern IQ test is built on the normal distribution — the famous "bell curve". The curve is anchored at two numbers: a mean of 100 and a standard deviation of 15. That means:
Your IQ score isn't "how many you answered correctly" — it's where your raw score lands on that curve, relative to your peers.
Professional batteries like the WAIS-IV and Stanford-Binet 5 break intelligence into multiple cognitive ability subtests, then combine them into a Full Scale IQ. The four most common subdomains are:
A short, well-designed online test like the one at quizvo.com samples from these same domains using pattern, logic, and verbal items — calibrated against population norms to produce a comparable score.
Before any IQ test is published, it's "normed" on a sample of thousands of test-takers. Statisticians map raw scores to standard scores using the bell curve. When you score 130, it doesn't mean you got 130% — it means you outperformed roughly 97.7% of the norming population. That's why IQ measurement works across age groups: a 9-year-old with an IQ of 120 didn't beat 30-year-olds — they outperformed 91% of other 9-year-olds.
Average IQ scores have risen roughly 3 points per decade for most of the 20th century — a phenomenon called the Flynn Effect. To keep the average pinned at 100, tests are re-normed every decade or so. That's why an IQ score from 1970 isn't directly comparable to one from 2026.
Your raw score on each subtest is converted into a standard score, then combined and scaled so the population mean is 100 with a standard deviation of 15. Your final IQ is your position on that distribution.
The scoring scale is identical — but the test items and norms differ. Children are compared to other children of the same age; adults to other adults. That's why IQ stays roughly stable across life even as raw cognitive ability changes.
By definition. Tests are calibrated so the median scorer in the norming sample lands at exactly 100. It's a statistical anchor, not an absolute measure.
A 20–30 question test sampling diverse cognitive abilities can give a strong estimate within ±5 points of a full clinical assessment, provided it's properly normed. Full WAIS testing is more precise but takes 90+ minutes and costs hundreds of euros.
Standard tests cap reliable measurement around 160. Above that, scores become statistical extrapolations rather than direct measurements — there simply aren't enough people in the norming sample to calibrate accurately.
Take the free 25-question Quizvo IQ test and find out exactly where you fall on the bell curve. Results in under 15 minutes.
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