Correlation and causation

Two things can change together without one causing the other. Yet patterns of this kind are often where a useful explanation begins. The challenge is to learn from the pattern without claiming more than it shows.

A correlation is an association between variables: knowing something about one is related to what we observe about the other. Causation concerns whether changing one thing would make a difference to another. This lesson explains the gap between those ideas and the evidence that can help bridge it.