Correlation Calculator
Calculate Pearson's r, Spearman's ρ, R², and the linear regression line from paired x,y data. Enter one pair per line.
| |r| Range | Strength | Cohen's Benchmark | Common in |
|---|---|---|---|
| 0.9 – 1.0 | Very strong | — | Physical sciences |
| 0.7 – 0.9 | Strong | — | Economics, education research |
| 0.5 – 0.7 | Moderate | Large effect (0.5) | Medical research |
| 0.3 – 0.5 | Weak | Medium effect (0.3) | Psychology, social science |
| 0.1 – 0.3 | Very weak | Small effect (0.1) | Large population surveys |
| 0.0 – 0.1 | No relationship | — | — |
Frequently Asked Questions
How is correlation taught differently around the world?
US AP Statistics: covers Pearson r, scatterplots, LSRL (least squares regression line), and residual plots. UK A-Level Psychology: Spearman's rho is typically taught alongside Pearson r, given psychology's use of ordinal data. IB Mathematics AA HL: regression and correlation including Pearson's product-moment correlation coefficient and significance testing. Germany Abitur: regression (lineare Regression) is a standard component of the probability and statistics section. Social sciences globally: Spearman ρ and Kendall's tau dominate when data is ordinal.
Does correlation prove causation?
No — this is one of the most important lessons in statistics worldwide. A strong correlation between X and Y could mean: X causes Y, Y causes X, a third variable Z causes both, or it's a spurious correlation (coincidence). Famous examples: ice cream sales correlate with drowning rates (both caused by summer heat). Shoe size correlates with reading ability in children (both caused by age). Establishing causation requires: controlled experiments with randomisation, intervention studies, or causal inference methods (Granger causality, instrumental variables).