Hot Reads: A NET Gain
Photo Credit: Aaron Babcock

Hot Reads: A NET Gain

August 23, 2018

It doesn’t have quite the resonance of “open the pod bay doors, HAL,” but I already like “show us the latest rankings, NET” better than I ever liked RPI.

NET being RPI’s replacement for the men’s basketball tournament selection committee. The NCAA announced the change on Wednesday.

The NCAA Evaluation Tool, which will be known as the NET, relies on game results, strength of schedule, game location, scoring margin, net offensive and defensive efficiency, and the quality of wins and losses. To make sense of team performance data, late-season games (including from the NCAA tournament) were used as test sets to develop a ranking model leveraging machine learning techniques. The model, which used team performance data to predict the outcome of games in test sets, was optimized until it was as accurate as possible. The resulting model is the one that will be used as the NET going forward.

The key difference worth noting here is that margin of victory is included in the new ranking system. That was a massive flaw of RPI, which is just a combination of a team’s winning percentage, that team’s opponents’ winning percentage and the opponents’ opponents’ winning percentage. Bad sign any time you need that many apostrophes just to explain the formula, but what did we expect? RPI was created in 1981. It had received updates over the years, but never the one that made the most sense –– including margin of victory.

It’s relevant information and, as Ed Feng of The Power Rank writes on his site, rankings systems that exclude it are limiting the value of the system.

The silliness of this restriction is mind boggling. Any algorithm that throws out this information has a lower class of predictive ability than one that uses margin of victory. It’s like setting up a shopping comparison website that only tells you which store has the lower price.

The NCAA has always had a problem with this due to fears of incentivizing “running up the score.” When the BCS debuted for the 1998 season the computer rankings used included margin of victory, but the powers that be quickly started to phase it out.

It wasn’t fully gone by 2001, however, and that may have had something to do with Nebraska’s last shot (to this point) at a national championship.

“In the 2001 season of the BCS, half of the eight computers used at that time considered margin of victory in their calculations, and the other half did not,” Jerry Palm wrote for a few years back. “That year, human poll No. 2 Oregon did not make the BCS title game due in large part to the fact that the MOV computers ranked the Ducks seventh, while the non-MOV versions ranked them third.”

However you felt about the selection of Nebraska over Oregon, then or now, it was enough for the BCS to go all-in on the MOV purge the following season. (Worth noting: The Ducks did go 5-1 in one-score games that season, though thumped Colorado in the Fiesta Bowl after being denied a shot at the Rose Bowl.)

College basketball is bringing MOV back, though not without instituting a 10-point limit on the calculation. A Nebraska win over Iowa by 20, for example, is treated the same as a win by 10. While I’ve never viewed running up the score as that much of a problem, it’s probably smart to build in some diminishing returns for margin of victory into any system.

That said 10 points doesn’t feel like that many points in basketball, but it’s better than what we had and I’m more than happy to see how it performs. A Sports Illustrated report indicated that the system received a trial run during the latter part of last season.

The system was optimized through a trial period during the late portion of the 2017-18 regular season and NCAA tournament. Results from several games were used as test sets to create a system that leveraged the machine's learning techniques.

Wait. Is there actually a “machine?” As in, one machine? The all-powerful NET computer, blinking away and computing college basketball results in some cooled room in Indianapolis?

I doubt it, but if so I like this system even more.

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