As any good Internet commenter will know, accuracy and precision are two subtly different things. But how do they differ, and why is it important?

In fact, accuracy is a measure of closeness while precision is a measure of reproducibility. That means that you can be accurate but not precise, or precise but no accurate. Or both, if you're lucky, or neither, if you're not.

But anyway. Rather than have me explain why that's the case, this neat little TED-Ed video does a very nice job of explaining the difference—and shows why it can be a matter of life and death. [TED-Ed]