Question
Can IQ tests be wrong?
Short answer
Yes. Every IQ score includes measurement error, often about plus or minus 5 points at 95% confidence on clinical tests. Scores can also be thrown off by fatigue, illness, distraction, unfamiliar item types, practice from an earlier attempt, outdated norms or a test that does not suit the person. A single score is an estimate.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
Error is built in
No test measures perfectly. Clinical full-scale IQ scores carry a standard error of a few points, so manuals report a confidence interval, often around plus or minus 5 points at 95% (Wechsler, 2008). A reported 108 is best read as probably somewhere from about 103 to 113. That is not a flaw in one test; it is true of every measurement of a person.
Try one · Pattern Recognition
Which tile comes next?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile shows a very large solid arrow pointing down and to the right (option 2).
How to solve it
- Compare neighboring tiles and name what changes each time.
- From tile to tile, the arrow turns an eighth of a turn counterclockwise.
- From tile to tile, the arrow gets bigger.
- Everything else stays the same from tile to tile.
- The last tile shows a large solid arrow pointing down. Apply each change once more.
- So the missing tile shows a very large solid arrow pointing down and to the right.
That was 1 puzzle. The full test has 25.
Things that push a score off
- The day itself. Poor sleep, illness, anxiety or interruptions lower performance.
- Familiarity. Retaking cognitive tests raises scores by about a quarter of a standard deviation on average, more when the same form is reused (Hausknecht et al., 2007). A second attempt can overstate ability.
- Old norms. Average raw performance drifted upward through the 20th century, by about 2.8 points per decade in a 2015 meta-analysis (Pietschnig & Voracek, 2015). A test normed long ago can give inflated scores today.
- The wrong scale. Some tests use a standard deviation of 16 or 24, so the same percentile prints as a different number (Wikipedia: IQ classification).
- A poor fit. A heavily verbal test can understate the ability of someone tested outside their first language; a nonverbal test can be a better match.
- A careless test. Many online quizzes have no norms at all.
How to get a more trustworthy number
Take the test once, rested, somewhere quiet, on a proper screen. Prefer tests that report a confidence range and explain their scoring. If a result matters for a decision, a supervised assessment by a psychologist is the right tool. See how accurate an IQ score is, why scores differ between tests and are online IQ tests accurate.
Sources
- Wechsler, D. (2008). WAIS-IV Technical and Interpretive Manual. Pearson.
- Hausknecht, J. P., Halpert, J. A., Di Paolo, N. T., & Moriarty Gerrard, M. O. (2007). Journal of Applied Psychology, 92(2), 373-385. doi.org/10.1037/0021-9010.92.2.373
- Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains. Perspectives on Psychological Science, 10(3), 282-306. doi.org/10.1177/1745691615577701
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification