I’ve been going through the book The Signal and the Noise, and pulling out some of the anecdotes in to contingency matrices. Chapter 6 covers margin of error and communicating uncertainty.

There’s a great anecdote in the opening of this chapter about flood heights and margin of error. If your levee is only built to contain 51 feet of water, then you REALLY need to know that the weather service prediction is 49 feet +/- 9, not just 49 feet.

This is bad enough, but Silver also points out that we almost never get a margin of error or uncertainty for economic predictions. This is probably why they’re all terrible, especially if they come from a politically affiliated group.

The lesson here is knowing what you don’t know is sometimes more important than knowing what you do know.