Glossary
Meta-analysis
Definition
A meta-analysis is a study of studies. It gathers the results of many separate studies on the same question and combines them into one overall estimate, usually giving more weight to larger and more precise studies. It smooths out the noise in any single sample.
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Why it matters for IQ scores
Many of the most quoted numbers about IQ come from meta-analyses, because single studies vary a lot by sample, country and test. Pooling them gives a steadier estimate and shows whether results agree.
Examples
- 271 samples, about 4 million people in 31 countries from 1909 to 2013: measured IQ rose about 2.8 points per decade, with gains slowing recently (Pietschnig & Voracek, 2015).
- 85 years of personnel research: general mental ability predicted job performance with a validity of 0.51 (Schmidt & Hunter, 1998).
- Retesting raised cognitive ability scores by about a quarter of a standard deviation on average (Hausknecht et al., 2007).
- Intelligence correlated about 0.56 with education, 0.45 with occupational level and 0.23 with income (Strenze, 2007).
Common confusions
A pooled average can hide real differences between groups or eras, which is why good meta-analyses also report how much results vary. And a meta-analytic correlation still describes groups, not you. See also validity, the negative Flynn effect, the Flynn effect and what IQ predicts.
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 tiny hatched diamond (option 4).
How to solve it
- Compare neighboring tiles and name what changes each time.
- From tile to tile, the diamond gets smaller.
- The fill cycles hatched, solid and outline, then starts again.
- Everything else stays the same from tile to tile.
- The last tile shows a small outlined diamond. Apply each change once more.
- So the missing tile shows a tiny hatched diamond.
That was 1 puzzle. The full test has 25.
Sources
- Pietschnig, J., & Voracek, M. (2015). One century of global IQ gains. Perspectives on Psychological Science, 10(3), 282-306. doi.org/10.1177/1745691615577701
- Schmidt, F. L., & Hunter, J. E. (1998). Psychological Bulletin, 124(2), 262-274. doi.org/10.1037/0033-2909.124.2.262
- 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
- Strenze, T. (2007). Intelligence, 35(5), 401-426. doi.org/10.1016/j.intell.2006.09.004