Sapiens Test

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What is an average IQ score? What your number actually means

The average IQ is 100. Always, in every country and every decade. That isn’t a discovery about people, it’s how the scale is built. Once you get that, you can read any IQ score in a few seconds.

Why it’s always 100

An IQ test doesn’t measure intelligence the way a scale measures kilograms. It counts your correct answers and compares them with a group of people who took the same test under the same conditions, the so-called norm group. Their scores are converted so the average lands on 100 and the standard deviation on 15.

So 100 is simply the middle of the group you were compared with. That’s why the first question about any IQ score is: compared with whom? Without an answer, the number means nothing. I wrote more about that in Are online IQ tests accurate?

What your score means

IQ scores fall on a bell curve, the normal distribution. Most people are close to the middle, and the further from 100, the rarer it gets. That lets you turn any score into the share of people you beat:

Roughly two thirds of people score between 85 and 115. The gap between 95 and 105 is noise, not a chasm. The same person can swing that much on two different days.

Mensa’s cutoff is the 98th percentile, the top 2% on a supervised test. On a scale with a standard deviation of 15, that’s 130.

Why different tests give different numbers

Because they don’t all use the same scale. Wechsler tests use a standard deviation of 15, Stanford-Binet 16 and the Cattell test 24. The same result, the top 2%, is 130 on Wechsler, 132 on Stanford-Binet and 148 on Cattell. If someone brags about an IQ of 148, it’s worth asking which test.

The second thing is how old the norms are. During the 20th century, test scores rose by about 3 points per decade (the Flynn effect), so a test with old norms inflates scores. The third is precision. A short test measures with an error of several points, so the honest way to report a score is as a range, not a single number.

What’s a good IQ score?

Honestly, 100 is a normal, average score and there’s nothing wrong with it. About one person in six scores above 115, one in fifty above 130. If a free online test gives all your friends 130 or more, you don’t have unusually brilliant friends. The scale is flattering them.

One more thing: an IQ score tells you how you did on this kind of task compared with other people, on that day. It doesn’t tell you what you’re worth.

How it works in my test

In Pattern you do 20 matrices in 20 minutes. Your score is your place among everyone’s first attempts, converted to the IQ scale once there are at least 50 attempts. With more results, you also see the range your score most likely falls in.

One caveat, because I’d rather say it myself: the people who play here like this kind of puzzle, so they’re not a random sample of the population. My 100 is the average player, not the average person.

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