Last week in Stat Corner powered by WrestleStat, we looked at the performance of Division I teams in one-point matches so far this season. We also introduced the possibility that one-point matches are decided, at least in part, by luck. This week, we follow up on that theory to see how various teams have performed over the last four seasons in one-point matches.
In case you’re not familiar with the theory from other sports, if one-point matches are decided by some element of luck, we should see teams that are very good or very bad in their one-point matches in a certain season regress towards the mean the following season. Luck should even out over time. If luck dictates that teams will, over a large enough sample size, win somewhere around 50% of their one-point matches, we should see the best and worst teams in one-point matches each season move towards a .500 record the next year. If instead, luck is little to no factor and one-point matches are decided largely by other factors, we should see the same teams continuing to finish away from .500.
To investigate this theory, we gathered the data from the 2013-14, 2014-15, and 2015-16 seasons as well as the updated information for this season. We’ll look at the top-eight and bottom-eight each season, eight being 10% of the Division I teams, to see how they fared the following year.
|Top 8||Bottom 8|
|Air Force||.722||.529||Old Dominion||.385||.522|
|The Citadel||.700||.367||Arizona State||.294||.432|
|As A Group||.748||.525||As A Group||.354||.554|
As a group, the top eight and bottom eight perform as we would expect if one-point matches are largely decided by luck. The best teams in the country at winning one point matches in 2013-14 won almost 75% of those matches, but only won 52.5% in 2014-15. Similarly, the worst eight teams in 2013-14 won a little more than 35% of their one-point matches but improved to winning more than 55% in 2014-15. There were some team outliers, though. Wyoming, Cornell, and Michigan State all did well two years in a row, though they all did regress a little bit. On the lower end, Utah Valley, Sacred Heart, and Arizona State remained below average both years. Utah Valley and Arizona State improved some while Sacred Heart remained the same.
It is certainly possible to have good or bad luck two years in a row, but these runs, if the luck effect is real, are unsustainable. It is interesting to note that Cornell (.517), Wyoming (.500), and Michigan State (.364), all experienced much more dramatic regressions in 2015-16. Utah Valley (.667) also saw their luck even out in 2015-16, but Arizona State (.426) and Sacred Heart (.300) both were down for a third consecutive year. Sacred Heart’s case may well be one of small sample size as they wrestled just 36 one point matches over those three seasons. Many teams get more than that in one year. Arizona State is harder to figure out, but they did finish much closer to the average in 2014-15 and 2015-16. The fact that they have won more than 80% of their one-point matches this season could indicate they had one of the longer runs of bad luck we’re likely going to see and are making up for it now.
|Top 8||Bottom 8|
|Northern Colorado||.684||.609||CSU Bakersfield||.281||.469|
|As A Group||.705||.598||As A Group||.363||.484|
Taking a look at the top and bottom eight from 2014-15, we see a similar trend with the group regressing towards the mean and all but one team making some move back towards .500. However, these results aren’t quite as dramatic as the last group. We should acknowledge that .500 would only be the average for every team if one-point matches were decided solely by luck and no other factor comes into play. That seems incredibly unlikely. There are probably teams who, over time, will win 60% of their one-point matches, just as some might only win 45%. However, it does appear, based on the data collected, that winning more than 65% or less than 40% is unlikely to continue as the sample size grows. Stanford, Rutgers, and Missouri are the clear outliers on the good side this time around, but none have won more than 60% of their one-point matches in 2016-17, with Rutgers and Missouri back under 55%. We discussed the Sacred Heart situation already and the other outlier on the low end, The Citadel, is over 50% in 2016-17.
So, how can we use this knowledge going forward? The simplest way is to identify teams who are performing outside of the sustainable ranges because we know, at some point, they are going to regress to the mean and win or lose more one-point matches than they have been. Below are the teams who, currently, are winning more than 65% of their one-point matches this season.
The most intriguing is Oklahoma State, of course, as they contend for a national title. The Cowboys didn’t finish any of the past three seasons above 66% which suggests, along with all the other data, that this current rate of success in one-point matches won’t last. Whether they regress in the next six weeks or make it through until next season is impossible to know, but it seems almost certain that their 16-3 record in one-point matches this season is partially aided by good fortune.
Who are the teams experiencing a run of bad luck?
|South Dakota State||.167|
Sacred Heart continues to struggle, though they still have wrestled only 43 one-point matches since the start of 2013-14. By comparison, 12 Division I teams wrestled more than that just last season. South Dakota State has only wrestled six one-point matches this season, but Iowa State is an abysmal 4-15 while Chattanooga is 4-12. The Jacks have won at least 47% of their one-point matches in each of the last three seasons while the Mocs haven’t been below 50% and were 18-8 a year ago. Expect both programs to catch some breaks soon.
In conclusion, it is clear that, as the sample size grows, Division I wrestling teams’ records in one-point matches tend to move towards .500. While runs of incredible success or frustrating losses will happen, teams will regress towards the mean eventually. This strongly suggests that luck is a factor in the outcome of one-point matches. While it is not the only factor, its effect is evident throughout the data. Teams that are currently performing at one of the extremes will have their luck turn. It is only a matter of time.