Glossary
Deviation IQ
Definition
A deviation IQ is a score based on how far your result sits above or below the average of your age group, measured in standard deviations and then rescaled so the average is 100 and one standard deviation is 15 points. Every modern IQ test reports this kind of score.
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How a deviation IQ is built
A test publisher gives the test to a large standardization sample at each age. For your age group it knows the average result and how spread out results are. Your result is then expressed as a z-score, the number of standard deviations from that average, and rescaled: IQ = 100 + 15 × z. David Wechsler introduced this approach with the Wechsler-Bellevue scale in 1939 (Wikipedia: WAIS).
An example
Suppose your result is 1.2 standard deviations above the average for your age. Your deviation IQ is 100 + 15 × 1.2 = 118. On the normal curve that is higher than about 88.5% of people your age. A result 0.4 standard deviations below average becomes 94, higher than about 34.5%.
Why it matters
The deviation IQ is why the average is always 100 and why a score keeps the same meaning at 20 and at 70. Scores are standardized within each age group (Wikipedia: Intelligence quotient), so they describe rank among peers. That is also why the age norms behind a test matter so much.
Common confusions
Some tests use a standard deviation of 16 or 24 instead of 15, so the same rank prints as a different number. The IQ percentile calculator handles all three. The history of how the deviation IQ replaced earlier scoring is in a short history of IQ tests.
Try one · Logical Reasoning
Which tile completes the second pair?
Tap the option you think is right, or show the answer.
Show the answer
The missing panel shows a large solid diamond, with small solid shapes: a circle at the bottom-left corner (option 5).
How to solve it
- Compare the first two panels and name exactly what changed.
- The main shape and the small shapes swap forms: the main shape takes the form of the small ones, and the small ones take the form of the main shape.
- Nothing else changes.
- Apply the same change to the third panel: a large solid circle, with small solid shapes: a diamond at the bottom-left corner.
- So the missing panel shows a large solid diamond, with small solid shapes: a circle at the bottom-left corner.
That was 1 puzzle. The full test has 25.
Sources
- Wechsler Adult Intelligence Scale. Wikipedia. en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale
- Intelligence quotient. Wikipedia. en.wikipedia.org/wiki/Intelligence_quotient