Possession-based Sports and Numbers (PSAN) Ratings

Evaluating the performance of basketball players using only the information available in boxscores is a very daunting task.  The formulas and explanations for every aspect of the ratings is not presented here.  But this page is an attempt to explain the concepts behind the ratings, enough to help you decipher what they are all about.

Visual Conceptual Overview of PSAN-Related Ratings

Click to See Full-Size Image

Expected Points per Possession (EPP)

The basis for much of the PSAN system is comparing the contribution of a player's actions against what his team was expected to do (or opponent was expected to attain) on each possession.  The EPP is calculated as "points divided by possessions."  If you're looking at a PSAN-related score for just a game, it would be the points and possessions from that game.  If you're looking at a season, it would be the entire season's points and possessions.

Possessions are calculated using a formula that is well-established in basketball statistical analysis: FGA - OREB + TO + 0.44*FTA

The bottom line here is that we can look at how a player's actions translate into points, and then compare each of his actions' point values to what was expected to happen on that possession.  That forms the basis for the value a player brings to his team.