Why is the average IQ 100 at every age?
An IQ score is read against people in the test-taker’s own age group. The average for each age group is 100, so this score describes a person’s standing among peers rather than a shared count of correct answers across all ages.
That is the basic idea behind average IQ. The figure does not mean that people of different ages solve the same problems or have identical skills. It tells you where a result falls relative to the group used to interpret it.
What changes with age: raw scores and norms
The number of items a person solves can change with age. This count, before a test’s norms are applied, is called a raw score. On its own, it does not show how a result compares with other people in the relevant age group.
Norms are used to interpret raw results against the appropriate age group. As a result, two people can solve different numbers of items and still have the same relative standing in their respective groups. The comparison depends on the test and the norms it uses. See how IQ tests work for more about how answers become a reported score.
Which age groups do WAIS and WISC cover?
WAIS is a Wechsler test for adults, and WISC is a Wechsler test for children. The publisher gives WAIS (IV and 5) an age range of 16 to 90 years and 11 months. WISC-V covers ages 6 to 16 years and 11 months.
These ranges describe the people the named tests are designed to assess. They do not mean all tests use the same age groups, norms, or items. A test for kids should be considered in relation to the age range and test it uses.
Why can a child and adult share an IQ score?
A child and an adult can have the same IQ score because each result is compared with the person’s own age group. The matching score means they have the same relative standing in their respective groups, not that they solved the same questions.
Their raw scores and answers can differ because each result is interpreted using norms for that age group. On the Wechsler scale, IQ scores have a mean of 100 and a standard deviation of 15.
What does an age-based IQ score tell you?
An age-based IQ score tells you how a result compares with the relevant norm group on that test. It does not give a direct count of what someone can solve, or make raw answers from different ages directly comparable. Its meaning depends on the test and its norms.
To read a result, consider the person’s age group, the test used, and the scale on which it is reported. IQClock offers a free timed reasoning exercise, but its free test does not print an IQ number. The IQ scale page explains how score ranges are described.