How causality differs from correlation?

Answer 1

Causality implies correlation; but correlation does not imply causality.

If some effect "A" is correlated with some other effect "B", it means that in cases where you observe "A" you also tend to observe "B", and vice versa.

If "A" and "B" are correlated, it might mean that "A" causes "B"; or it might mean that "B" causes "A"; or it might mean that some third factor causes both "A" and "B".

For example; it may be that church attendence is correlated with good health. This might mean that attending church causes you to be healthy; or it might mean that if you're already healthy then you're more likely to attend church. Or, it might mean that some third factor (for example, living in an affluent neighborhood) causes people both to be more healthy and to attend church more often.

For another example, it may be that consumption of lemonade is correlated with sunburn. This does not necessarily mean that lemonade causes sunburn, or that sunburn causes people to drink more lemonade; more likely, it means that a third factor (such as hot weather) causes an increase in both.

To demonstrate that "A" causes "B", you need to show first that "A" precedes "B" in time; and you also need to show that if you perform an experiment in which you remove "A" (while keeping all other factors the same), then "B" also decreases.

Answer 2

correlation is the statistical relation between 2 factors which are variable. Correlation occurs ANY time they vary together in a regular enough way.

A great example is that drinking water and eating ice cream both increase together in the summer. This means both factors are correlated, in fact positively correlated (they vary the same way).

Causality means what caused what and that is a matter for practical reasoning, not statistics. In the case of ice cream and water we expect that there is a third factor, the weather which causes both.

Correlation does not mean or show causality: in an experiment or comparison you may find correlation wwhich suggests there may be a relationship but it does not SHOW
that one thing caused the other, or reveal which caused which if they did. That requires rational reasoning...

Answer 3

Causality (causation) states that Factor X *causes* Factor Y. Correlation simply states that Factor X and Factor Y are related.

Two things can be correlated without one causing the other, but you can not have a causal relationship without a correlation between the factors.

Answer 4

Causality is the affected. Correlation is the comparison.