|Relative Percentage Index (RPI)|
The Relative Percentage Index (RPI) is widely used to produce power ratings. Unlike most power rating systems, the RPI does not consider margin of victory or how well a team has played. It only considers whether a team won or lost. In fact, the RPI is based entirely on winning percentage.
It essentially measures a teamís strength of schedule and how a team does against that schedule. It is based 25% on a teamís winning percentage, 50% on the winning percentage of their opponents, and 25% on the winning percentage of their opponentís opponents.
Rating Percentage Index (RPI) Formula=.25*(Team's Winning Percentage)+.50*(Opponents' Average Winning Percentage)+0.25*(Opponents' Opponents' Average Winning Percentage)
For example if;
Atlanta is 4-1 (W/L Pct= .800)
Atlanta's opponents averaged a 12-8 (W/L Pct.= .600) record
Atlanta's opponents' opponents averaged a 64-16 (W/L Pct = .800) record, then,
RPI for Atlanta is = (0.25 * .800) + (0.5 * .600) + (0.25 * .800)=.700
Comments: It is best known for its use in college sports. Rarely is it mentioned in NBA circles because all teams play each other and most of the time people have fairly similar schedules.