What is Correlation?
We live in a world full of numbers, trends, and charts. News headlines, social media posts, and even school textbooks tell us that “X causes Y.” But a lot of the time, the facts don’t really justify the headline statements, and it’s all because of two concepts that are usually confused – correlation and causation.
One of the most important principles that underpin critical thinking is this: just because two things happen together (correlation) doesn’t mean one caused the other (causation).
The shorthand for this “correlation does not imply causation”. And once you understand it, you start seeing it everywhere. A correlation is simply when two or more things happen at the same time.
Ice Cream and Violence?
Let’s look at the classic example. Studies have apparently shown that when ice cream sales go up, so do rates of violent crime. That sounds worrying, can it possibly be true that eating ice cream makes people violent?
What’s really going on is that both things increase in hot weather. When it’s warmer, more people buy ice cream than during cold weather, obviously! And as we know, people are also more likely to be outdoors when it’s hot. And it’s also the case that when people are outside in large numbers getting all overheated, tensions can run higher, and crime rates can rise.
The warm weather causes both the increase in ice cream sales and the rise in crime.
This is why we must be careful before claiming that one thing causes another, just because they happen together. It could be true that one causes the other, but that has to be demonstrated using other information. The correlation itself doesn’t necessarily prove anything.
Why This Matters for Children
Today’s children are grown up in a world of social media algorithms, AI and rampant misinformation. More than ever, children need to learn critical thinking in order to discern truth and wisdom from untruths and idiocy. Helping our children understand the difference between correlation and causation is an important part of this.
Asking the Right Questions
We should encourage our children to ask right questions, such as:
- What’s the evidence for this?
- Is there another way we can interpret the evidence?
- How do we know one thing caused the other?
