What is a deviation IQ score and how is it interpreted in modern testing?

• A. A score with mean 0 and SD 1.
• B. IQ score calculated only from verbal tasks.
• C. An IQ score with a mean of 100 and standard deviation of 15; deviations from 100 indicate relative standing in the population.
• D. A score not standardized.

Answer: (C)

Deviation IQ is the standardized scoring method used in modern IQ testing. Tests are normed so that the average score is set at 100 and the spread is a standard deviation of 15. This means your score shows how far above or below the average you are, measured in units of standard deviation, rather than just a raw point total. Interpreting it is about relative position within the population: a score of 100 is typical for your age group, 115 is one standard deviation above the mean (roughly the top 15%), 130 is two standard deviations above (about the top 2%), and 85 is one standard deviation below (roughly the bottom 15%). This scaling allows fair comparisons across ages and groups, since the mean and spread are held constant across the normative sample.