Noted advanced basketball statistics expert and author Dr. Dean Oliver has singled out four factors that help an NBA team win games. These four factors, with their relative weights in parenthesis, are: Shooting (40%), Turnovers (25%) Rebounding (20%), Free Throws (15%).
He identified these factors after years of research and many other advanced statisticians agree with the list, though some disagree with the weight. To calculate the defensive four factors, one uses the statistics of the opposing team to gauge how well the team in question performs. Shooting is measured using the Effective Field Goal Percentage: (FG + 0.5 * 3P) / FGA. Turnovers are measured using the Turnover Percentage: TOV / (FGA + 0.44 * FTA + TOV). Rebounds are measured using the Defensive Rebound Percentage: DRB / (Opp ORB + DRB). Lastly, free throws are measured using the Free Throw Percentage: FT/FGA.