2023 REPORT 9: AN ILLUSTRATION SHOWING WHY THE CURRENT NCAA RPI IS DEFECTIVE AND THE EFFECT OF THE DEFECT PART 2

In the previous post, I used Quinnipiac and Nebraska during the 2022 season to illustrate why the current NCAA RPI is defective and the potential effects of the defect on NCAA Tournament at large selections.  As shown in that post, the defect is in how the current NCAA RPI formula computes Strength of Schedule.  That SoS computation results in teams’ RPI ranks and their ranks as Strength of Schedule contributors often being quite different, when logically they should be the same.  This is a defect that the Balanced RPI corrects.

Again using the 2022 season, when I apply the Balanced RPI rather than the current NCAA RPI to the season’s results, there are eight teams that become candidates for at large selection (Top 57 in the rankings) that were not under the current NCAA RPI.  The following table shows those eight teams.  Also, for each of them, the table shows (1) using the current NCAA RPI, the average rank of its opponents and the average Strength of Schedule contributor rank of its opponents and (2) using the Balanced RPI, the opponents’ average rank and average Strength of Schedule contributor rank.  [In the table, ARPI 2015 BPs is the current NCAA RPI and URPI 50 50 Sos Iteration 15 is the Balanced RPI.]

As you can see, in every case the current RPI formula significantly underrates Strength of Schedule as compared to the opponents’ RPI ranks.  5 of these teams are from the West, 1 from the Middle, and 2 from the South regions.  6 are from Power 5 conferences and 2 from a strong non-Power 5 conference, in other words all are from strong conferences.

Matching these eight teams are eight other teams that are in the candidate pool under the current NCAA RPI but not under the Balanced RPI.

Of these, 3 are from the South, 2 from the Middle, 2 from the North, and 1 from the West regions.  2 are from Power 5 conferences and 6 are from non-Power 5 conferences, in otherwords they are predominantly from non-Power 5 conferences.  As the table shows, the current NCAA RPI underrates the 2 Power 5 conference teams’ Strengths of Schedule as compared to their current NCAA RPI ranks, overrates 2 non-Power 5 teams’ Strengths of Schedule as compared to their current NCAA RPI ranks, and gets 4 non-Power 5 teams’ Strengths of Schedule about right as compared to their current NCAA RPI ranks.

In considering the differences between the current NCAA RPI ranks and the Balanced RPI ranks in these tables, it is important to remember that the same Strength of Schedule measurement problem you are seeing for the above teams also affects all other teams.  The Balanced RPI ranks are based on correcting the strength of schedule problem for all teams.  The differences you see between the Balanced RPI ranks and the current NCAA RPI ranks are the result of all of those corrections.