2025 ARTICLE 4: THE NCAA RPI AND ITS EFFECT ON NCAA TOURNAMENT SEEDS

In  2025 Article 3, I showed how powerful the NCAA RPI is in the NCAA Tournament at large participant selection process.  In this article, I extend that discussion to show the power of the NCAA RPI in the NCAA Tournament seeding process.  I also, at the end, will summarize the data in Article 3 and this article.

This article assumes that you have reviewed Article 3, particularly for an explanation of the "Standards" and "Standards Plus Tiebreaker" systems I use as ways to show the relationship between the season's game results data, the factors the Women's Soccer Committee considers when forming the NCAA Tournament bracket, and the Committee's actual decisions.

#1 Seeds

The following table shows the 7 most "powerful" factors when it comes to the Committee's selection of #1 seeds.  I measure a factor's power, for example in relation to #1 seeds, by considering how many of the factor's seeds would match the Committee's seeds if the NCAA simply awarded seeds based on that factor.

As you can see, for #1 seeds, the NCAA RPI, by itself, can "pick," on average, between 3 and 4 #1 seeds per year.  Further, all of the most powerful factors include the NCAA RPI.

The following table shows the NCAA RPI number of teams picked by year and also includes the number when applying the Standards and Standards Plus Tiebreaker systems.  Since the NCAA RPI is the most powerful single factor for #1 seeds, that is the Tiebreaker factor in the Standards Plus Tiebreaker system for #1 seeds.

The Standards system (the three white columns) is useful for getting a picture of how the Committee might go through the #1 seed selection process.  The "In" Selections column is teams that are clear #1 seeds based on past history.  The Open Positions column is the number of additional teams the Committee needs to pick to fill out the seed group.  The Candidates for Remaining Open Positions column is the number of teams the Committee has to choose from to fill the open positions -- these are teams that have no aspects of their profiles that say "yes, a team with this profile always has gotten a #1 seed" and also none that say "no, a team with this profile never has gotten a #1 seed."  Thus in 2007, as an example, according to the Standards system 3 #1 seeds were clear, with 1 open position and 2 candidates to fill the position.  This happens to match the Median situation over the years: 3 clear #1 seeds, leaving 1 open position to be filled from 2 candidates (see the Median row at the bottom of the table).

The Standards With Tiebreaker system takes the open position(s) candidates and ranks them using the Tiebreaker, with the best-ranked candidate(s) filling the open position(s).  Since the NCAA RPI is the best factor at picking #1 seeds, that is the tiebreaker for the #1 seed Standards Plus Tiebreaker system.  As you can see from the column on the right, the Standards Plus Tiebreaker system picks match 97.1% of the Committee's picks -- in other words all but 2 of the 68 #1 seeds over the years.

#2 Seeds

As you can see, again the most powerful factor is teams' RPIs.  In the table, CO stands for Common Opponents and HTH for Head to Head, referring to the NCAA factors of results against common opponents and head to head results.

The RPI, on its own, would fill correctly 64.7% of all #2 seeds.  This is considerably fewer than the percentage for #1 seeds.  It means that in filling #2 seeds, the Committee is significantly influenced by the RPI but also by other factors.

As with the #1 seeds, the Standards system fills about 3 positions per year, leaving 1 position to be filled from 2 candidates.  The Tiebreaker again is teams' RPIs.  The Standards Plus Tiebreaker system correctly fills 92.6% of the #2 seeds, having missed 5 of the 68 #2 seeds over the years.

#3 Seeds

The RPI continues to be the most powerful factor.

You can see that the Committee's #3 seed picks are less predictable, for all the systems.

#4 Seeds

The RPI remains the most powerful factor.

As you can see, the #4 seeds show a continuing decline in the systems' ability to predict seeds.

#1 to #4 Seeds as a Group

It will help to see how the systems match up with the Committee's #1 through #4 seed decisions, when considering teams as a group without reference to which of those seeds they get.

As the tables show, the RPI itself and the Standards Plus Tiebreaker system do a quite good job of matching with the Committee's decisions on which 16 teams will share the #1 through #4 seeds, with the Standards Plus Tiebreaker missing a median of only 1 of the 16 positions per year.

#5 to #8 Seeds as a Group

With the NCAA having had #5 through #8 seed pods only since 2022, there are not enough data to do meaningful breakdowns like the above for each of those pods.  The following tables show data for the four pods as a group, although in my opinion there still are not enough data to draw firm conclusions.

It is important to note that this table suggests that the RPI, for the #5 through #8 seeds, by itself is not the most powerful decision factor.  Rather, the paired NCAA RPI Rank and Top 50 Results Score factor is the most powerful.  Significantly, this relates to the information in 2025 Report 3, which shows that the paired NCAA RPI Rank and Top 50 Results Rank factor is the most powerful for at large selections.

As this table shows, the Committee's #5 through #8 seeds as a group appear to be pretty data driven, with the Standards Plus Tiebreaker system being a quite good indicator of which teams will be in the group.  It will take more years' data, however, to reach firmer conclusions on this.

Summary

The following table summarizes the above tables as well as the At Large tables from 2025 Article 3:

The RPI is the most powerful factor the Committee considers when it comes to #1 and #2 seeds and which teams will be in the #1 through #4 seed group as a whole.  From the larger seed group, which teams will get #3 and #4 seeds appears to be somewhat data driven but also appears to be somewhat random.

For the #5 through 8 seeds and particularly for at large selections, the Standards system plus the paired RPI and Top 50 Results factors as a tiebreakers give a good match to the Committee's decisions.  Since the Top 50 Results scoring system relates to teams' RPI ranks, the RPI plays a significant role in both halves of the paired factor.

From an overall perspective, the RPI appears to be a critical factor in all of the "close" decisions the Committee must make.