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Why do most IQ scores fall between 85 and 115?
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intelligence test
Overview of human intelligence, including a discussion of intelligence tests.
Intelligence test scores, often referred to as IQ scores, follow an approximate normal distribution. This statistical pattern means that the majority of scores cluster around the average, with fewer scores occurring as you move further away from the center.
Specifically, on the IQ scale:
* Approximately two out of every three scores fall between 85 and 115.
* About 19 out of every 20 scores fall between 70 and 130.
This distribution is a result of how IQ tests are standardized. An average IQ score is set at 100, and the scores are designed to spread out symmetrically around this average. Therefore, scores between 85 and 115 represent the most common range, encompassing the average performance and scores slightly above and below it.1