correlate

Correlate is a verb meaning to show a relationship or connection between two or more things. In everyday use, to correlate two phenomena is to observe that they occur together or vary in a related way.

In statistics, to correlate means to measure the strength and direction of association between variables. The most common measure for linear relationships is the Pearson correlation coefficient, r, which ranges from -1 to 1. Values near 1 indicate a strong positive linear relationship, values near -1 indicate a strong negative linear relationship, and values near 0 suggest little or no linear association. For nonparametric or monotonic relationships, Spearman's rho and Kendall's tau are often used.

Important caveats accompany correlation analysis. Correlation does not imply causation; a high correlation may reflect a direct causal link, reverse causation, or the influence of a confounding variable. Spurious correlations can arise in large datasets. Researchers use experimental designs, temporal data, regression analysis, and techniques such as partial correlation to investigate potential causal pathways and to control for third variables.

Correlate can also function as a noun in technical writing, referring to a factor that is closely related to another. For example, a correlate of disease risk is an associated factor identified in studies. The term is common across disciplines including statistics, epidemiology, psychology, and data science, where it helps describe patterns of association and forms the basis for further inferential work.