NCAA Tournament Bracket Formation: Most Important Factors for At Large Selections

Following up on the preceding post, here is a table showing the 26 most important factors for the Committee's NCAA Tournament at large selections:

Factor	Yes at Large
ARPI Rating and Top 50 Results Rank	144
ARPI Rank and Conference Rank	128
ARPI Rank and Rating	115
ARPI Rating	115
ARPI Rating and Top 60 CO Rank	109
ARPI Rank and Top 50 Results Rank	109
ARPI Rank	107
ARPI Rating and ANCRPI Rank	107
ARPI Rating and Top 60 CO	89
ARPI Rank and ANCRPI Rank	89
ARPI Rank and Top 60 CO Rank	87
ARPI Rank and Top 60 CO Score	69
ANCRPI Rank and CO Score	61
Top 50 Results Rank and CO Score	60
ARPI Rating and ANCRPI Rating	59
ARPI Rating and Top 50 Results Score	58
Top 60 CO Score	57
CO Score and CO Rank	54
ARPI Rank and Conference Standing	49
ANCRPI Rank and CO Rank	46
ARPI Rating and Last 8 Games (Poor Results)	46
Top 60 CO Rank	45
Conference ARPI and CO Score	43
Top 50 Results Rank	43
Conference Rank and CO Rank	41
ANCRPI Rank and Top 50 Results Rank	41

To provide context for this table, as stated in my previous post, realistically the pool of teams the Committee looks at for seeding and at large selection purposes is the top 60 teams in the ARPI rankings, thus a total of 600 teams over the last 10 years (less the 3 teams in the top 60 over the last 10 years with records below 0.500).  Over the last 10 years, there have been 155 Automatic Qualifiers in the top 60.  Since the AQs are not in competition for at large selections, the actual pool of teams the Committee is looking at for at large selections is roughly 445 teams, in other words roughly 44.5 teams per year.  From this pool, the Committee had to pick 34 teams per year from 2007 through 2013 and 33 teams per year since then (due to the split between the Big East and American Athletic Conferences).

The above table shows that the ARPI Rating/Top 50 Results Rank paired factor is the most important factor for purposes of saying "yes" a team gets an at large selection.  The Top 50 Results Score and Rank factors use a scoring system that rewards teams for wins and ties against teams ranked #50 or better by the ARPI.  The scoring system is weighted strongly in favor of good results against very highly ranked teams.  This paired factor is significantly more powerful than any other factor.

Next in terms of power is the ARPI Rank/Conference Rank paired factor, which is significantly more powerful than the next factors on the list.  Then come the ARPI Rating factor by itself and the ARPI Rank/ARPI Rating paired factor, which are significantly more powerful than the ones below them.  And then come four factors, one of which is the ARPI Rank factor by itself, the other three of which are either either ARPI Rating or ARPI Rank paired with one of Top 50 Common Opponents Rank, Top 50 Results Rank, or Adjusted Non-Conference RPI (ANCRPI) Rank.  The other factors on the list are significantly weaker than any of these.

Altogether, the list demonstrates the importance of teams' ARPI ratings/ranks in the at large selection process and, of the other primary factors, the importance of the Top 50 Results factor.  It also is noteworthy that the Head to Head Results factor does not show up on the "top 26" list, at all.

What about the "no" at large selection factors?  Here's a list of the top 26 factors:

Factor	No at Large
ARPI Rank and Top 50 Results Rank	41
ARPI Rank and Top 50 Results Score	40
ANCRPI Rank and Top 50 Results Rank	32
ARPI Rating and Conference Rank	32
ARPI Rank and Conference Rank	26
ARPI Rating and Top 50 Results Score	25
ARPI Rating and Top 50 Results Rank	24
ARPI Rating and ANCRPI Rank	24
ANCRPI Rating and HTH Score	24
ARPI Rank	23
ARPI Rating and Top 60 HTH	21
ARPI	20
Top 50 Results Score and HTH Score	20
Top 50 Results Rank and HTH Score	20
ARPI Rank and Rating	19
ARPI Rank and Top 60 HTH Score	16
ANCRPI Rank and HTH Score	16
HTH Score and CO Rank	16
Top 60 HTH	16
Conference Rank and HTH Score	15
HTH Score and CO Score	15
ANCRPI Rating and Conference ARPI	15
ARPI Rating and Top 60 CO Rank	14
ANCRPI Rating and Conference Rank	14
ANCRPI Rank and Top 50 Results Score	12
Conference ARPI and HTH Score	12

Once again, teams' ARPI Ratings and Ranks, coupled with their Top 50 Results Ranks, are the most powerful factors, by a good margin.  Of interest, ARPI Ratings and Ranks, coupled with a team's Conference Rank, also are powerful factors.

It's worth noting that the most powerful factors, by themselves, are not close to sufficient to do the entire job.  The Committee currently needs to select 33 at large teams from a pool of roughly 44.5 teams per year.  The most powerful "yes" factor can select 14.4 teams per year.  The most powerful "no" factor can exclude 4.1 teams.  This leaves the Committee with 26 teams still in the pool, from which to fill 18.6 remaining at large slots.  Thus the other factors are needed to whittle this number down to a few slots each year to be filled from the remaining pool of a few teams that meet no "yes" and likewise no "no" factor patterns.  Nevertheless, the most likely factors to get a team a "yes" and also to get a team a "no" are the paired ARPI/Top 50 Results factors.