Glossary
Intelligence quotient (IQ)
Definition
An intelligence quotient, or IQ, is a standardized score from an intelligence test. It shows how your performance compares with people your own age, on a scale where the average is 100 and one standard deviation is 15 points. It describes rank, not a count of right answers.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
Where the term comes from
Alfred Binet and Theodore Simon published the first practical intelligence test in 1905, and William Stern proposed the term “intelligence quotient” in 1912 (Wikipedia: Intelligence quotient). The word quotient stuck even though modern tests no longer divide anything. Since David Wechsler introduced the deviation IQ in 1939, scores have been standardized against a reference group instead (Wikipedia: WAIS).
How to read an IQ number
An IQ places you on a curve. On the standard scale the mean is 100 and the standard deviation is 15, so a score of 115 sits one standard deviation above average and is higher than about 84.1% of people. A score of 85 sits one standard deviation below and is higher than about 15.9%. The IQ score chart lists every score from 55 to 160 with its percentile.
Common confusions
An IQ is not a percentage of questions answered correctly, and it is not a fixed property stamped on a person. It is a test result with measurement error, compared with a particular group of people at a particular time. Two tests can print different numbers for the same person if they use different scales or norms. When IQ Octopus reports a score, it calls it an estimated IQ for that reason. For the bigger picture, read what an IQ test measures.
Try one · Quantitative Reasoning
Which number comes next?
3, 6, 10, 15, 21, 28, ?
Tap the option you think is right, or show the answer.
Show the answer
The next number is 36 (option 1).
How to solve it
- Find the gaps between neighbors: 3, 4, 5, 6, 7.
- The gaps between the numbers grow by 1 each time.
- So the next gap is 8, and 28 + 8 = 36.
That was 1 puzzle. The full test has 25.
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale