We all like to look at rankings of women's basketball teams (who's the best team? how many teams are better than us?), but looking at rankings instead of the underlying ratings scores loses information about how much better one team is than another.
It's been agreed that there is no dominant team this year, but is there a group of teams that have separated themselves from the pack? To address this, I looked at the Massey rating score, the Massey power score, the RPI score, the Elo score and the Her Hoops Stats score.
Prior to the UConn-Oregon game, the Massey rating score suggested that three or four teams, Baylor, South Carolina, Oregon and maybe Connecticut were separating from the pack (first page of the attached pdf file [137 Kb]). The Massey power score looked about the same (second page), with South Carolina and Oregon flipped. The similarity is as expected, as the Massey rating score is derived from the Massey power score, with the former intended to measure past performance and the latter intended to measure potential for the future.
The RPI score includes information about strength of schedule and opponents' strength of schedule. I have argued in the Massey Analytics thread on the General Women's basketball forum that this does not address how good a team is. Others have pointed out in the same thread that these inclusions may well be beneficial to NCAA women's basketball as a whole. Since my goal is finding a group of teams that are better than the rest, I'm going to take the RPI with a grain of salt. Prior to the UConn-Oregon game, the RPI (third page) was in partial agreement with the Massey score. Oregon and South Carolina were separating from the pack, with Baylor and Connecticut in a large group of second-tier teams (which also included Louisville, Stanford, Gonzaga, UCLA, Maryland, Missouri St, Oregon St and Iowa).
The results for Elo were more similar to the Massey scales, with Baylor, South Carolina, Oregon separating from the back and Louisville, Stanford and Connecticut forming a group of second-tier teams (fourth page). Her Hoops Stats had only Baylor, Oregon and South Carolina in the elite group and Connecticut and Maryland as second-tier teams (fifth page).
I sought a consensus among these five scales using Principal Component Analysis. Setting aside the details about PCA, the resulting composite score was essentially the sum of the individual scale scores, after each scale was transformed to have a mean of zero and a variance of 1, multiplied by 1/sqrt(5). The composite had Baylor, Oregon and South Carolina separating, with Connecticut not far behind (sixth page).
And then UConn played Oregon ...
After that game, the Massey rating score had only Baylor, Oregon and South Carolina in a group far ahead of everyone else, with Connecticut among fourteen second-tier teams (seventh page). The Massey power score was similar, except that Baylor and Oregon were flipped (eighth page).
The RPI score had only Oregon and South Carolina separated, without a clearly separated group of second-tier teams (ninth page). Similar to the Massey scores, Elo had Oregon, Baylor and South Carolina separating, but only Louisville and Stanford were in the second-tier teams (tenth page). HHS had Baylor and Oregon flipped, with Connecticut and Maryland in a distant second cluster (eleventh page).
The composite score had Oregon, Baylor and South Carolina as the elite teams, with no clearly separated group of second tier teams (eleventh page).
If short, according to these five rating scales, there appears to be three elite teams now: Oregon, Baylor and South Carolina. Each of the five scales had these teams as elite, with the exception of RPI excluding Baylor (due to their extremely weak out of conference schedule). The outcome of the UConn-Oregon game has moved UConn out of elite or near elite status, and further back towards the pack. The South Carolina games will provide UConn with an opportunity to move back to the elite group.
Notes:
It's been agreed that there is no dominant team this year, but is there a group of teams that have separated themselves from the pack? To address this, I looked at the Massey rating score, the Massey power score, the RPI score, the Elo score and the Her Hoops Stats score.
Prior to the UConn-Oregon game, the Massey rating score suggested that three or four teams, Baylor, South Carolina, Oregon and maybe Connecticut were separating from the pack (first page of the attached pdf file [137 Kb]). The Massey power score looked about the same (second page), with South Carolina and Oregon flipped. The similarity is as expected, as the Massey rating score is derived from the Massey power score, with the former intended to measure past performance and the latter intended to measure potential for the future.
The RPI score includes information about strength of schedule and opponents' strength of schedule. I have argued in the Massey Analytics thread on the General Women's basketball forum that this does not address how good a team is. Others have pointed out in the same thread that these inclusions may well be beneficial to NCAA women's basketball as a whole. Since my goal is finding a group of teams that are better than the rest, I'm going to take the RPI with a grain of salt. Prior to the UConn-Oregon game, the RPI (third page) was in partial agreement with the Massey score. Oregon and South Carolina were separating from the pack, with Baylor and Connecticut in a large group of second-tier teams (which also included Louisville, Stanford, Gonzaga, UCLA, Maryland, Missouri St, Oregon St and Iowa).
The results for Elo were more similar to the Massey scales, with Baylor, South Carolina, Oregon separating from the back and Louisville, Stanford and Connecticut forming a group of second-tier teams (fourth page). Her Hoops Stats had only Baylor, Oregon and South Carolina in the elite group and Connecticut and Maryland as second-tier teams (fifth page).
I sought a consensus among these five scales using Principal Component Analysis. Setting aside the details about PCA, the resulting composite score was essentially the sum of the individual scale scores, after each scale was transformed to have a mean of zero and a variance of 1, multiplied by 1/sqrt(5). The composite had Baylor, Oregon and South Carolina separating, with Connecticut not far behind (sixth page).
And then UConn played Oregon ...
After that game, the Massey rating score had only Baylor, Oregon and South Carolina in a group far ahead of everyone else, with Connecticut among fourteen second-tier teams (seventh page). The Massey power score was similar, except that Baylor and Oregon were flipped (eighth page).
The RPI score had only Oregon and South Carolina separated, without a clearly separated group of second-tier teams (ninth page). Similar to the Massey scores, Elo had Oregon, Baylor and South Carolina separating, but only Louisville and Stanford were in the second-tier teams (tenth page). HHS had Baylor and Oregon flipped, with Connecticut and Maryland in a distant second cluster (eleventh page).
The composite score had Oregon, Baylor and South Carolina as the elite teams, with no clearly separated group of second tier teams (eleventh page).
If short, according to these five rating scales, there appears to be three elite teams now: Oregon, Baylor and South Carolina. Each of the five scales had these teams as elite, with the exception of RPI excluding Baylor (due to their extremely weak out of conference schedule). The outcome of the UConn-Oregon game has moved UConn out of elite or near elite status, and further back towards the pack. The South Carolina games will provide UConn with an opportunity to move back to the elite group.
Notes:
- In order to manage the overstrikes, I used a smallish font in the plots and rounded all of the scores to three significant digits. Since the attached file is a pdf, you can zoom in to your heart's desire.
- The Massey ratings were obtained from the Massey site: Massey Ratings - CBW. Here's an oddity: the cutoff for inclusion in the ratings is games played by 11:59 pm EST. Hawaii played a home game on 1/30 that was scheduled at 7 pm local time, which is midnight on 1/31 EST. That game was not included in the 1/31 report.
- I'm getting HHS ratings from the Her Hoops Stats site: Her Hoop Stats Rtg National Team Leaderboard | NCAA Division I Women's Basketball | Her Hoop Stats.
- I'm getting the Elo rating from Warren Nolan site: ELO Chess Ranking 2020 Womens College Basketball | WarrenNolan.com.
- Lastly, I'm getting the RPI data from the Warren Nolan Site: RPI (Live) 2020 Women's College Basketball | WarrenNolan.com. The RPI rankings are given on that page (twice), but the RPI score for each team is only on the team site. It takes about 2-3 minutes for my program to retrieve the rankings for 351 teams. It would be easier to get them from the Real Time RPI site, but I have lost faith in quality of their data. For about 3 1/2 weeks in January 2020, they included UConn's loss to Louisville on 1/31/18 (no, we didn't play Louisville this season, that's a game from last season). RTRPI finally fixed that, but they're still including Savannah State in the rankings, a school that in no longer in the MEAC, having made the transition from Division I to Division II this year and has no games scheduled against Division I opponents.
- All programming and analysis was done in R.
. It turns out, as they said in Star Wars, there is another: Washington State. For UConn, all three were non-conference. For Washington St, Oregon was a conference game and the other two were self-inflicted.
