The NFCA, in conjunction with mathematician Warren Nolan, will once again release a ratings percentage index (RPI) for Division I softball. The first rating was released April 3, with the No. 1 team in the USA Today/NFCA Division I Top 25 Poll, Florida, atop the RPI.
2009 NFCA Simulated Ratings Percentage Index
The Gators are 34-3 through games of Sunday, March 29, 2009. The Southeastern Conference leads the Conference RPI at the first date of release.
What is the RPI?
The RPI is a mathematical calculation used to help determine teams’ success, using a calculated strength of schedule and won-loss percentage.
The NCAA develops its own RPIs to give selection committees another tool when selecting teams for the NCAA championships. This year, the NCAA will release its softball RPI on a bi-weekly basis, with the first one released on March 31. The NFCA and NCAA RPIs are a little different since the NCAA uses bonuses and penalties that it does not release to the general public.
“We first developed the RPI in the 2005 season as a benefit for our members, since the NCAA was not making its RPI available to coaches,” said NFCA Executive Director Lacy Lee Baker. “Although the NCAA will release an RPI this year during the season, we think the NFCA weekly compilation and the strength of schedule is still interesting and helpful. From reports we’ve received from the softball community, it’s apparent that coaches and fans agree,” Baker continued.
In addition, the NFCA RPI also is used as a tool by voters in the USA Today/NFCA Coaches poll, and by the coaches and committee members selecting Louisville Slugger All-Region and All-American teams.
The same basic formula is used in NCAA Division I men’s and women’s basketball, baseball and softball; however, there are minute differences (penalties and bonuses) that are specific to each sport. For example, there may be a small penalty if a Division I school plays a non-Division I opponent. There may be a small bonus for beating a top 25 team.
When determining the RPI for each team, the following basic formula is used:
25% -- Winning percentage.
50% -- Opponents’ winning percentage.
25% -- Opponents’ opponents’ winning percentage.
Although the NCAA publishes the basic formula, it does not release the mathematical bonuses and penalties specific for each sport. It is important to note that the NFCA RPI may not be exactly the same as the NCAA RPI, since the NCAA will not release its bonus and penalty calculations. However, the two should be close and the NFCA RPI should be an indication of where a team stands. The NCAA does not endorse the NFCA RPI.
What are the procedures used in developing the NFCA RPI?
To prepare an RPI, the mathematician must have every score in the nation. All of the 30 conferences that sponsor softball agreed to send the NFCA an XML file. The XML files, which are prepared weekly by conference personnel to send their conference members’ game statistics and scores to the NCAA, are developed through the scoring program, The Automated Scorebook.
Scores for these conferences, as well as independents, are gathered by the NFCA and sent to the mathematician in a special format.
The NFCA has selected Nolan, a mathematician who is involved in calculations for football’s Bowl Championship Series, to calculate the RPI. He also publishes his own basketball and baseball RPI.
Nolan receives the XML files and other scores by Wednesday. After the information is proofed and corrected by the NFCA, the RPI is published on NFCA.org on Fridays. Therefore, the RPI is not final until Fridays.