Media & PR

Correlation implies causation rather more often than you might think

Chances are, you’re very familiar with the idea that correlation does not mean causation, as nicely illustrated by this cat:

It’s a point I’ve made a good few times on this blog too, such as in relation to web browsers and murder rates, not to mention mountain ranges and murder rates.

But as I point out in my new book, Bad News:

This wise advice quickly ossifies into misplaced repetition, too often deployed in situations where it is not applicable.

Consider salt (or pepper, if you prefer). When you season your food, it makes it taste saltier, right? I will go out on a limb and guess every reader agrees.

But why do you believe that? After all, the combination of putting salt on food and it being saltier is just correlation, and you know that correlation does not imply causation. So, you shouldn’t really believe that putting salt on your food makes it saltier (and therefore taste more delicious to you), should you?

Unless you’ve got a friend to blindfold you, split your food in two, put salt on one and not the other, and then see how you perform in a double-blind randomised trial – or unless you’ve hunted out the research of someone else who has done this – you are just relying on correlation implying causation.

And that is just the sort of daft error you are smart enough to avoid making, right?

Find out all about when correlation does imply causation, including the pioneering work of Austin Bradford Hill, who saved millions of lives, in Bad News: what the headlines don’t tell us, available for pre-order from Waterstones, Hive or Amazon.


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