Correlation is the relatedness of two factors. It's measured by [[Correlation Coefficient]], which ranges from -1 to +1, where 0 is "no correlation". I forget how to do it by hand, but it's one of those things that nobody does by hand. Excel makes it very easy with `correl(...,...)` # Correlation ≠ Causation Correlation does not _**necessarily**_ imply causation. Clearly, if A *causes* B you expect to see a correlation, but the simple correlation isn't enough to assume a causal relationship between the variables. If `A` and `B` are correlated, it could be that: - `A` causes `B` - `B` causes `A` - `A` and `B` are both caused by a 3rd factor - It's a pure coincidence and they're unrelated[^1] ![[Pasted image 20250118114434.png]] ## Visualizing Correlations are best seen in [[Scatter Chart]]s, and what [[Pairwise Plot]]s are all about. Also there are [[Fourfold Contingency Table]]s. Note that [[Statistical Summaries May Hide Truths]]. **** # More ## Source - [XKCD](https://m.xkcd.com/552/) for the comic ## Related [^1]: With the advent of [[Big Data]] and the ability to capture and compute millions of factors, you're bound to come across completely unrelated yet very similar looking results.