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What does an IQ score of 100 represent?
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intelligence test
Overview of human intelligence, including a discussion of intelligence tests.
An IQ score of 100 represents the average intelligence for a given age group. This is because IQ scores are typically designed to follow a normal distribution, with 100 being the midpoint.123
Historically, IQ was calculated as the ratio of a person's mental age to their chronological age, multiplied by 100. In this system, a score of 100 meant that a person's mental age was the same as their chronological age. While many modern tests no longer use the concept of mental age, they still standardize scores so that 100 remains the average. Approximately two-thirds of people score between 85 and 115 on IQ tests.132