Question
What is IQ?
Short answer
IQ (intelligence quotient) is a score from a standardized test of reasoning and problem solving. Modern tests set the average for each age group at 100 with a standard deviation of 15, so about 68% of people score between 85 and 115. An IQ shows how you did compared with people your own age.
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Where the name 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 early score really was a quotient: a child's mental age divided by their age, times 100. Today's tests no longer divide anything, but the name stuck.
How a modern IQ score works
Since David Wechsler introduced the deviation IQ in 1939 (Wikipedia: WAIS), IQ has been a standard score. A test is given to a large sample of people of each age. Their results set the scale: the middle of each age group becomes 100, and one standard deviation becomes 15 points (Wikipedia: Intelligence quotient). Your score then says where you sit in that spread.
Because the scale is built on the normal curve, the share of people at each score follows from math. About 68% of people score between 85 and 115, about 95% between 70 and 130, and about 99.7% between 55 and 145 (the 68-95-99.7 rule). You can look up any score in the IQ score chart or convert it with the percentile calculator.
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a large outlined triangle pointing up, with small solid shapes: a triangle at the left side (option 1).
How to solve it
- Compare the first two panels and name exactly what changed.
- The whole figure turns a quarter turn counterclockwise.
- The large shape becomes outlined.
- Nothing else changes.
- Apply the same changes to the third panel: a large hatched triangle pointing right, with small solid shapes: a triangle at the top.
- So the missing panel shows a large outlined triangle pointing up, with small solid shapes: a triangle at the left side.
That was 1 puzzle. The full test has 25.
What the labels mean
Test publishers attach plain-language labels to score ranges. On the WAIS-IV, 90 to 109 is Average, 110 to 119 High Average, 120 to 129 Superior and 130 and above Very Superior (Wikipedia: IQ classification). The labels are shorthand for a position on the curve, not a judgment of a person. The classification guide covers all seven bands.
What IQ leaves out
An IQ test samples reasoning, memory, speed and knowledge with a set of timed tasks. It does not measure creativity, character, motivation or practical skill, and any single score carries measurement error. For the bigger picture, see what intelligence is and what an IQ test measures.
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- 68-95-99.7 rule. Wikipedia. en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale