## Wednesday, April 06, 2016

### 2015 Yards Per Play: Mountain West

Only four more conferences to go in our 2015 recap. This week we go over the Mountain West. Here are the 2015 Mountain West standings.
So we know what each team achieved, but how did they perform? To answer that, here are the Yards Per Play (YPP), Yards Per Play Allowed (YPA) and Net Yards Per Play (Net) numbers for each Mountain West team. This includes conference play only, with the championship game not included. The teams are sorted by division by Net YPP with conference rank in parentheses.
College football teams play either eight or nine conference games. Consequently, their record in such a small sample may not be indicative of their quality of play. A few fortuitous bounces here or there can be the difference between another ho-hum campaign or a special season. Randomness and other factors outside of our perception play a role in determining the standings. It would be fantastic if college football teams played 100 or even 1000 games. Then we could have a better idea about which teams were really the best. Alas, players would miss too much class time, their bodies would be battered beyond recognition, and I would never leave the couch. As it is, we have to make do with the handful of games teams do play. In those games, we can learn a lot from a team’s Yards per Play (YPP). Since 2005, I have collected YPP data for every conference. I use conference games only because teams play such divergent non-conference schedules and the teams within a conference tend to be of similar quality. By running a regression analysis between a team’s Net YPP (the difference between their Yards per Play and Yards per Play Allowed) and their conference winning percentage, we can see if Net YPP is a decent predictor of a team’s record. Spoiler alert. It is. For the statistically inclined, the correlation coefficient between a team’s Net YPP in conference play and their conference record is around .66. Since Net YPP is a solid predictor of a team’s conference record, we can use it to identify which teams had a significant disparity between their conference record as predicted by Net YPP and their actual conference record. I used a difference of .200 between predicted and actual winning percentage as the threshold for ‘significant’. Why .200? It is a little arbitrary, but .200 corresponds to a difference of 1.6 games over an eight game conference schedule and 1.8 games over a nine game one. Over or underperforming by more than a game and a half in a small sample seems significant to me. In the 2015 season, which teams in the Mountain West met this threshold? Here are the Mountain West teams sorted by performance over what would be expected from their Net YPP numbers.
Only one team saw their actual record differ significantly from their expected record based on their YPP differentials. And boy did it ever differ. For the second time in three seasons, Hawaii finished winless in Mountain West play. The 2013 team also posted decent YPP numbers and improved to three league wins in 2014, so there is hope for new coach Nick Rolovich. So how did Hawaii go about losing all their conference games despite bad, but not horrendous YPP numbers? Close games are not the culprit, as Hawaii only lost a single one-score league game (by a single point at New Mexico). No, turnovers told the story for the Warriors. Hawaii turned the ball over 26 times in their eight conference games, while only forcing six of their own. Their in-conference turnover margin of -20 was by far the worst in the conference (13 worse than second to last Wyoming). We’ll discuss more about this historic margin later. I am not making the argument that Hawaii was a ‘good’ team in 2015. They were shut out in each of their first three road games (albeit against strong competition in Ohio State, Wisconsin, and Boise State). However, they did show signs of life early in the year by beating Colorado of the Pac-12 thanks to a little assist from some bumbling officials. If their turnover margin was merely bad and not historically poor, the Warriors probably would have scrounged up at least one and potentially a pair of conference wins.

Hawaii was not the only Mountain West team with a historical in-conference turnover margin in 2015. While Hawaii was struggling with a -20 margin, San Diego State was rolling through the conference en route to an undefeated record and league title with a +19 turnover margin (excluding their championship game win over Air Force). To get a handle on what one might expect from these two polar opposites going forward, I decided to look at teams with similar extreme in-conference turnover margins and see how they performed the following year. Here we’ll define extreme as averaging two more or two less turnovers per game that your opponent. For an eight game conference schedule, that would equate to a turnover margin of +16 or -16. Similarly, for a nine game schedule that would be either +18 or -18. Hawaii and San Diego State were certainly unique in 2015. Only ten other teams since 2005 posted such an extreme turnover margin (Arkansas State also fit the criteria, but like the Warriors and Aztecs, their follow up performance is unknown at this time). We’ll start with the teams with extreme negative turnover margins.
Obviously, teams with extremely poor turnover margins don’t tend to win a lot of games. These four squads combined to go 2-28 in conference play. Perhaps not surprisingly, three of the teams had new head coaches the following year. Oklahoma State elected to retain their head coach (probably since he was in his first season), and that has worked out pretty well for the Cowboys. New Mexico State is a bit of an oddity, as they became a college football independent after their turnover plagued final season in the WAC. That is why there is no follow up conference record listed for them. As for the other three teams, well, they all improved their conference record by at least two games with Oklahoma State and Wyoming qualifying for bowls. For what it’s worth, New Mexico State’s overall record improved from 1-11 to 2-10, so each member of the quartet improved the next season. A pessimist might point out each team had nowhere to go but up after their poor showings and a statistician might highlight the small sample size here. However, another statistician might bring up something about regression (or in this case progression) to the mean and opine that an extremely poor turnover performance is unlikely to be repeated. As for me, I would set the over/under on league wins at two for Hawaii in 2016.

Now let’s look at the other side of the coin. Here are teams with extreme positive turnover margins.
In a not too surprising development, teams with historically great turnover margins tend to have good records. These six teams combined to go 47-3 with Oregon and Toledo being the only teams to not win a conference title. Unlike the poor turnover teams there was continuity at the head coaching position the following season with only Oregon losing their head coach (to the NFL no less). For the most part, each team remained strong the next year with only Kansas State falling out of contention for a conference title. Each team qualified for a bowl game in the following season and two thirds of the teams declined by one game or less. An optimist would likely say these teams had nowhere to go but down after compiling their pristine conference records, and once again, a point can be made about small sample sizes. However, as with Hawaii, San Diego State is unlikely to see their extreme turnover margin repeated. The Aztecs did not throw a single interception in conference play last year! While I expect them to be contenders in the conference in 2016, expecting another undefeated, scorched earth run through the Mountain West is likely folly.