NFL Stat Metrics for Beginners
A reference guide for those familiarizing themselves with football data analytics
Figure 1: A chart of expected points (EP) values based on the offense's yardline and down.
I use lots of different terms for NFL statistics in my projects. The table below will serve as a reference to clear up any confusion that readers may have while analyzing my work.
| Metric | Definition | Context/Usage |
|---|---|---|
| Expected Points Added (EPA) | Expected Points Added: The difference between a team's expected points after a play vs. before the play. | Measures play-by-play efficiency rather than just yards. |
| Success Rate (SR) | The proportion of plays in a given sample that have a positive EPA value. | A balanced alternative to EPA (which swings wildly on a play-by-play basis) to measure offensive consistency |
| Completion Percentage Over Expected (CPOE) | The regression between a QB's completion percentage and the mean expected completion percentage of their pass attempts based on difficulty. | Isolates a QB's accuracy from their scheme or receiver talent. |
| Expected Pass Rate (xPass) | An algorithmically predicted likelihood of a passing play based on game state (score, down, etc.) | Used to evaluate QB performance in predictable vs. unpredictable situations. |