Basketball Statistics 101: Four Factor Model

Chapter 28 is called basketball stats 101: The four factor model and this chapter describes how basketball stats are tracked, which stats are important and how individual players and teams should be assessed based on stats.

The NBA box score is the official way that game stats are kept track of. You can see how each player is performed and also how the team performed as a whole.

Effective field goal percentage is measured by the formula :  All Field Goals Made + .5 (3 Point Field Goals Made)/(All Field Goal Attempts). It is a better metric to understand how effective a team or players shooting actually is because it gives 3 point shots made 50% more credit. Winston shows an example where the new York Knicks shoot 50 for 100 where 1 out of 5 three pointers are made  which gives an effective field goal percentage of 50.5% while the Mavs shoot 45/100 but an impressive 15/20 three pointers which yields an EFG of 52.5%. At first sight it looks like the Knicks are shooting a higher percentage because they made more baskets, but in reality the Mavericks have shot better because of the improved 3 point shooting.

In essence shooting numbers are deceptive because of the three point line but the EFG metric clears this up by making 3 pointers worth 50% more.

Rebounding in the NBA can be misleading also because the numbers can be inflated due to really good shooting or really bad shooting which yields more or less opportunity for a rebound. There are two metrics that separate rebounding into two categories. Offensive rebounding percentage measures the amount of rebounds gained on offense and defensive rebounding % measures the amount of rebounds gained on defense. Coaches and General managers can have a better idea of a players rebounding tendencies on both ends of the floor.

Team offense and Team defense are analyzed as two separate components. Winston talks about the 4 main factors for team offense that should be measured to understand how a team performs. These factors are Effective field goal percentage, turnovers committed per possession, Offensive rebounding percentage, and free throw rate.

Defense can also be measured. The 4 factors for team defense are the opponent’s effective field goal percentage, defensive turnovers caused per possession, defensive rebounding percentage and opponent’s free throw rate.

Winston put these factors into a regression analysis and the results show that the 4 factors are virtually uncorrelated.

In the NBA there are many ways to be successful and also ways to fail. Winston lays out how 4 teams in 2007 either were successful or failed based upon key stats. Each team had major differences.

Winston ran a regression analysis to determine how important the 4 factors really are and which ones were directly correlated to win percentage. The variables used were:

It became apparent that shooting percentage is the most important factor for an NBA team to be successful.