What is the Pearson correlation coefficient?
What is the Pearson correlation coefficient?
The Pearson correlation coefficient (r) is the most widely used correlation coefficient and is known by many names:
- Pearson’s r
- Bivariate correlation
- Pearson product-moment correlation coefficient (PPMCC)
- The correlation coefficient
The Pearson correlation coefficient is a descriptive statistic, meaning that it summarizes the characteristics of a dataset. Specifically, it describes the strength and direction of the linear relationship between two quantitative variables.
Although interpretations of the relationship strength (also known as effect size) vary between disciplines, the table below gives general rules of thumb:
| Pearson correlation coefficient (r) value | Strength | Direction |
|---|---|---|
| Greater than .5 | Strong | Positive |
| Between .3 and .5 | Moderate | Positive |
| Between 0 and .3 | Weak | Positive |
| 0 | None | None |
| Between 0 and –.3 | Weak | Negative |
| Between –.3 and –.5 | Moderate | Negative |
| Less than –.5 | Strong | Negative |
The Pearson correlation coefficient is also an inferential statistic, meaning that it can be used to test statistical hypotheses. Specifically, we can test whether there is a significant relationship between two variables.
