Deviation Intelligence Quotient (IQ) is a way of measuring an individual’s generalized intelligence. It uses statistics to analyze a person’s intelligence relative to their age. Deviation IQ is scored based on how an individual deviates from the average IQ of 100. It measures IQ as a normal distribution with the average IQ being a 100 with a standard deviation of +/- 15.
This differs from the original way of measuring IQ which was using a ratio score which compared a person’s “mental” age with their actual age. Deviation IQ scores are intended to be more accurate and account for people who have very high scores on intelligence measures.