Correlation does not imply causation

Correlation does not imply causation

Here's why and what you should know about it.

It is a common misunderstanding to assume that one thing is the consequence of another because they happen together.

People do it all the time.

Sometimes, they don't do it on purpose, they just don't see the difference or make an error.

Sometimes, they highlight correlation to falsely imply causation, which is simply dishonnest.

In any case, thinking that correlation implies causation is incorrect.

Let us be clear. Things may happen together because one is the consequence of the other. So, people are right when saying that correlation may be a hint of causation.

Nonetheless, one has to be careful and rigorous. A lot of things happen together, even though they do not cause each other. For example...

A study showed that for French kids, being named Kevin was correlated to getting poor grades in school. Of course, your name does not have a direct effect on your grades. In that case, the correlation is caused by a common source.

See the comments under that graph showing the correlation between the person being CEO of Microsoft and the stock price and the analysis here for another example of a correlation not being a proof of causation.

Try to figure out if there is a causation effect, and if so, in what direction, in this article about the correlation between sexual activy and salary.

So what?

Well... just keep that in mind and learn to detect and point at fallicious arguments like the ones discussed here. It will be useful on a daily basis:

Let people around you know when you hear a weak argument based on correlation. Be a constructive critic, and help us make the world a better place.

Thank you.

Start now!

Share this with your friends to help spread the word.

Want more?

There are good articles to learn more on Wikipedia and on RationalWiki.

You can find some humor on the topic on XKCD and Gizmodo.


My name is Christian Roy. I created this page as an exercise to teach me some basic web skills. I also wrote this as my humble contribution to help people discuss more inteligently.

You can read more from me on my blog (mostly in French) or on Twitter (English and French).

Feel free to contact me if you have any questions or comments about this page.

Creative Commons License
This work by Christian Roy is licensed under a Creative Commons Attribution 3.0 Unported License.