Why did my IQ score change?

Why do IQ scores differ between tests? Learn why it's normal for intelligence test scores to vary due to measurement error, different tasks, and statistical factors like regression to the mean.

1. All psychological tests have a degree of “measurement error,” which is the amount of randomness that is part of test scores. Because RIOT IQs and IQs from other tests have some randomness in them, it is unrealistic to expect IQs from different tests (or even the same test) to be exactly the same.
2. Different tests contain different tasks. Although every intelligence test measures g, there is no such thing as a pure measure of g. By using verbal, spatial, speed, and other tasks to measure intelligence, every test measures some cognitive abilities that are different from general intelligence. These other abilities contribute to IQ. If the RIOT and the other test do not contain many overlapping tasks, then the mix of non-g abilities that each test measures will cause differences in IQ.
3. A statistical phenomenon called “regression toward the mean” can also cause score differences, especially among people with extremely high or extremely low scores. When regression toward the mean occurs, later scores are more average than earlier scores. If your previous IQ score was very high (or very low) and your RIOT IQ is more average, then you could be experiencing regression toward the mean. Regression toward the mean is a purely statistical occurrence and does not reflect actual intelligence changes.