Glossary
Mean
Definition
The mean is the arithmetic average of a set of scores: add them all up and divide by how many there are. IQ tests are built so that the mean score of each age group in the reference sample is exactly 100, which is why an average IQ is 100 by definition.
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Why it matters for IQ scores
Every IQ score is a distance from the mean. Modern tests standardize scores to a mean of 100 and a standard deviation of 15 within each age group (Wikipedia: Intelligence quotient), so 100 always means “exactly average for your age”. A score of 112 tells you how far above that point you landed, measured in standard deviation units.
An example
If five people score 92, 98, 100, 104 and 106, the mean is 500 divided by 5, which is 100. On a full IQ scale the mean sits in the middle of the WAIS-IV Average band, 90 to 109, which holds about 49% of people on the normal curve (Wikipedia: IQ classification).
Common confusions
“The mean is 100” is a property of the scale, not a finding about how smart people are. The mean is also tied to a reference group at a particular time, which is why tests are restandardized: see standardization sample and what is the average IQ. For the spread around the mean, read about the normal distribution, or see what an IQ of 100 means.
Try one · Pattern Recognition
Which tile comes next?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile shows four hatched crosses (option 1).
How to solve it
- Compare neighboring tiles and name what changes each time.
- From tile to tile, one more cross is added.
- The fill cycles hatched, outline and solid, then starts again.
- Everything else stays the same from tile to tile.
- The last tile shows three solid crosses. Apply each change once more.
- So the missing tile shows four hatched crosses.
That was 1 puzzle. The full test has 25.
Sources
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification