Kevin Drum Accused of Obeying the Law

On Friday night I snarked that the NAEP folks—who produce the “gold standard” of student testing—couldn’t even count to two:

Muphry’s Law states that “If you write anything criticizing editing or proofreading, there will be a fault of some kind in what you have written.” Sure enough, a regular reader emails to say that I got this wrong. Here are the exact numbers:

  • 2015 score: 265.4, which rounds to 265.
  • 2017 score: 266.6, which rounds to 267.
  • Difference: 1.2, which rounds to 1.

This is actually a really nice example of how rounding numbers can get you into trouble. And it means that I have to change my criticism from NAEP’s too-weak arithmetic skills to its too-strong adherence to house style. Obviously their house style for simple graphics like this is to use only whole numbers. That’s probably a good style rule. But accuracy and clarity are always your main goal, and there are rare occasions when you just have to make style exceptions. Here’s what the chart should have looked like:

Maybe there’s another way to do this, but one way or the other, the graphic simply can’t be allowed to display what looks like an obvious error. In long rows of numbers, you sometimes see the disclaimer “does not add to 100 due to rounding,” or something similar. Maybe something like that would be enough. But I suspect that the cleanest and clearest way of getting this right is to break the style rule. I sympathize with style nazis, since I tend to be one myself, but every once in a while house style rules just have to be broken.

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