Quick Correlation and Causality: A Scientist's Perspective

[clane]

Hello All,

I am trying to look at some correlation numbers and while I am aware that correlation does not always indicate causality can a correlation coeffiecent that is very near to zero be used to indicate that it is not a cause?

Thanks

C

 

[mathman]

Elementary logic should give you the answer.

Causality => correlation.

Therefore: not correlation => not causality.

 

[EnumaElish]

Let's be careful.

Causality does not always imply correlation because the relationship may be nonlinear. Correlation is a linear relationship.

If two variables are dependent, their relationship can be linear or nonlinear. If it's linear, their correlation will be significant. If their corr. is not significant, then you can say that the variables are not LINEARLY dependent on each other. But, they can still be non-linearly dependent.

So the answer is technically "No, a zero correlation does not mean no causality." A more roundabout way of putting it is: "A zero correlation would imply no causality only if a non-linear relationship can be excluded on other grounds."