Rating Percentage Index - Popularized by college basketball, the RPI is a simple measure used to determine the strength of teams. Factors used to calculate RPI are a team's record, a team's strength-of-schedule, and their opponents' strength-of-schedule.
Strength-of-Schedule - The difficulty of opposition played, as valued by winning percentage.
Pythagorean Performance - Based on the work of Bill James, Pythagorean Performance measures the variance in a team's won-loss record to the team's Pythagorean Expectation. Pythagorean Expectation uses the number of goals scored, the number of goals allowed, and the number of games played to determine a team's expected Won-Loss record. A positive value is an indicator of over-performance, while a negative value suggests under-performance.
Margin-of-Victory Per 60 Minutes - By taking each team's goal difference and dividing by the number of minutes played, we're able to compare margin-of-victory statistic regardless of the length of game played.
Simple Rating System - Taking into account the average margin-of-victory and strength of schedule for each team, SRS is a predictive statistic to compare teams. The difference in SRS between two teams is the expected margin-of-victory between those teams at a neutral site.