Glossary
Correlation
Definition
A correlation is a number from -1 to 1 that describes how closely two measures move together across a group. At 1 they rise together perfectly, at 0 there is no straight-line link, and at -1 one falls as the other rises. Correlations describe groups, not individuals.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
Why it matters for IQ scores
Nearly every claim about what IQ relates to is a correlation. Reading them well is the difference between a fair summary and an overstatement.
Real examples
- General intelligence at age 11 and total GCSE points at 16: 0.81, in about 70,000 English children (Deary, Strand, Smith & Fernandes, 2007).
- General mental ability and job performance: 0.51, across 85 years of research (Schmidt & Hunter, 1998).
- Intelligence with education about 0.56, with occupational level about 0.45, and with income about 0.23 (Strenze, 2007).
These are very different strengths. A correlation of 0.81 is strong; one of 0.23 is modest, with huge overlap between people of different scores.
Common confusions
A correlation is not a percentage, and it does not tell you what will happen to one person. It also says nothing about cause on its own. For how these numbers fit together, read what IQ predicts, and what it does not and does IQ predict success? Related terms: validity and meta-analysis.
Try one · Abstract Reasoning
Which tile completes the grid?
Tap the option you think is right, or show the answer.
Show the answer
The missing tile has one solid triangle (option 2).
How to solve it
- Start with the first row and name what changes from tile to tile.
- Every row and every column contains each shape (diamond, triangle and square) exactly once.
- Every row and every column contains each number of shapes (one, two and three) exactly once.
- The fill (solid) stays the same in every tile.
- Check the rules on the second row, then apply them to the third.
- So the missing tile has one solid triangle.
That was 1 puzzle. The full test has 25.
Sources
- Deary, I. J., Strand, S., Smith, P., & Fernandes, C. (2007). Intelligence, 35(1), 13-21. doi.org/10.1016/j.intell.2006.02.001
- Schmidt, F. L., & Hunter, J. E. (1998). Psychological Bulletin, 124(2), 262-274. doi.org/10.1037/0033-2909.124.2.262
- Strenze, T. (2007). Intelligence, 35(5), 401-426. doi.org/10.1016/j.intell.2006.09.004