Precision vs. accuracy

You never know where you’ll stumble over some good writing advice. This week I stumbled into a technical paper on analytical instrumentation systems. Stick with me. This will make sense in a minute.

When laboratory technicians want to analyze a sample of something, they want the results to be accurate. They also want the results to be precise. What’s the difference? The technical paper explained it this way:

Imagine someone shooting at a target. If the resulting holes cluster in a tight group, we can say that the shooter is precise. A shooter who sprays bullets all over the place is not precise at all.

But where is that tight group of holes from our precise shooter? If the cluster sits on the outer ring instead of the bull’s eye, the shooter is not very accurate. A tight grouping in the center of the target shows that the shooter is both precise and accurate.

You can apply the same idea to your writing.

You could say that 84,968 people attended the Super Bowl game last month, which would be a very precise number. But it would be inaccurate, because the actual attendance was 70,807. You’d be off by 20 percent.

Or you could round the actual attendance to the nearest 10,000 and say that 70,000 attended. That’s not nearly as precise, but it’s 99 percent accurate. (Or 98.86 percent, if you want to be more precise about the accuracy.)

Some writers, especially the unscrupulous ones, will throw a lot of precise statements at you in the hope that you’ll mistake them for being accurate. Don’t fall for such dishonesty, and please don’t ever employ it.

Anton Chekhov shows how to be both precise and accurate in this snippet: “The dam, flooded with moonlight, showed not a bit of shade; on it, in the middle, the neck of a broken bottle glittered like a star.”

“Flooded with moonlight” is accurate, while “the neck of a broken bottle glittered like a star” is precise. Putting the two together gives the reader a vivid picture of the scene.

That’s precisely what you should strive for.


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