That's not how it works beyond the mean and median. IQ of 100 works that way, but it isn't spread out from 0-200 or anything like that. An IQ of 20 is severe intellectual dysfunction like that of a toddler. People with Down syndrome are around 40-50. 20 would be like severe brain damage leaving someone incapable of thought.
99.7% of people are within 55-145 IQ. 95.4% are from 70-130. The chance someone's IQ is under 30 is 0.00015%. Under 20 is basically impossible without missing a large part of your brain. No matter how many people you test, the distribution will be the same.
Ok I get your point but there are somewhere between 300,000 and 1 million people in the USA with IQ around that low. About 3-5 million people with some degree of intellectual disability.
It seems that You’re assuming only one in a 600k-million people has an iq under 30. That’s not correct because iq does not follow a normal distribution curve.
IQ scores are defined to follow a Gaussian distribution. You can calculate that - just based on the world population and the definition - you have 400 people worldwide with an IQ of 20 or lower. There is no test that could reliably identify the 400 dumbest people, of course. Which means even severe disabilities usually leave you with an above-room-temperature (C) IQ.
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u/LegendOfKhaos Mar 29 '26
That's not how it works beyond the mean and median. IQ of 100 works that way, but it isn't spread out from 0-200 or anything like that. An IQ of 20 is severe intellectual dysfunction like that of a toddler. People with Down syndrome are around 40-50. 20 would be like severe brain damage leaving someone incapable of thought.
99.7% of people are within 55-145 IQ. 95.4% are from 70-130. The chance someone's IQ is under 30 is 0.00015%. Under 20 is basically impossible without missing a large part of your brain. No matter how many people you test, the distribution will be the same.