Brier score

The Brier Score grades a forecaster's ability to predict outcomes. Like a weather man's ability to predict rain the next day.

The score is computed as $S = \frac{1}{N}\sum_{i}^{N}(f_i - x_i)^2$, where $f$ is the predicted odds of something happening, (70% chance to rain would be 0.7,) and $x$ is the outcome (1 if correct, 0 otherwise).

The Brier score requires that predictions meet three criteria.