The Signal and the Noise: Why So Many Predictions Fail-but Some Don't

by Nate Silver

The Finnish scientist Hanna Kokko likens building a statistical or predictive model to drawing a map.68 It needs to contain enough detail to be helpful and do an honest job of representing the underlying landscape—you don’t want to leave out large cities, prominent rivers and mountain ranges, or major highways. Too much detail, however, can be overwhelming to the traveler, causing him to lose his way. As we saw in chapter 5 these problems are not purely aesthetic. Needlessly complicated models may fit the noise in a problem rather than the signal, doing a poor job of replicating its underlying structure and causing predictions to be worse. But how much detail is too much—or too little? Cartography takes a lifetime to master and combines elements of both art and science. It probably goes too far to describe model building as an art form, but it does require a lot of judgment.