Give Now

A Moment of Science

Baseball, Tar, and the Scientific Method

One of the fundamental ideas of scientific thinking can be summed up in the phrase: "Correlation does not imply causation." That can be very confusing.

Did children playing baseball cause this tar to become soft?

Baseball, tar, and the scientific method, on this Moment of Science.

One of the fundamental ideas of scientific thinking can be summed up in the phrase: “Correlation does not imply causation.” A simpler way to say that is: “this follows that” does not mean “this follows from that.”  Even in science, it’s easy to confuse the two.

Let’s look at an example. Suppose you notice that sometimes the tar in the pavement outside your house is soft and pliable, while other times it’s hard and brittle. This is an observation of the world, what a scientist would call “a datum”. By checking the tar every day for a reasonable period of time, you may discover a pattern: whenever the kids next door play baseball, the tar goes soft. Repeat the experiment to be sure: yes, you will find, there is a statistically significant linkage between these events, no matter what method of data analysis you use. Have we not just proven that the baseball affects tar?

No, we haven’t; and the reason is that the connection here is still one of correlation. Our observation of the tar and the kids is entirely valid scientific practice, as far as it goes; however, the leap to causation — that is, to the conclusion that baseball causes tar to soften — is invalid.

You’ve probably guessed already what the real link in our scenario is: both these things happen when the sun comes out. But the distinction between correlation and causation in less obvious situations is often a tricky one — and something scientists have to keep in mind all the time.

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science