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30 Oct 2013

FEI Week 9: Game Factors

by Brian Fremeau

Last week we went under the hood of the FEI ratings to understand why FEI is so smitten with the Pac-12 and Utah in particular. As predicted, Utah’s non-blowout loss to USC over the weekend did little to diminish the Utes’ standing in the FEI ratings. Utah has faced six FEI top-30 opponents to date and has two FEI top-10 victories. Stanford has faced five top-30 opponents. All other FEI top-25 teams have faced an average of only 2.4 top-30 opponents each. Four top-25 teams -– Florida State, Baylor, Ohio State, and Oklahoma State –- have faced zero top-30 opponents.

This week I wanted to go even further under the hood and reveal the opponent-adjusted game-by-game data for every team. The philosophy behind the FEI ratings has been published here and has not changed: teams are rewarded for playing well against good teams, win or lose, and they are punished more severely for playing poorly against bad teams than they are rewarded for playing well against bad teams. How does this philosophy apply to the raw data collected and processed each week?

At the game level, the primary unit of measure is Game Efficiency, a measurement of the success of teams maximizing their own scoring opportunities and limiting the success of their opponent scoring opportunities over the course of the non-garbage possessions in the game. In the FEI formula, those raw individual game measures are adjusted for the strength of the opponent faced to produce GFEI, a single-game measure of the overall performance. I discussed GFEI a bit at the end of last season after Alabama posted the best GFEI rating of the last decade in the 42-14 victory over Notre Dame in the national championship game.

The FEI formula does not take a simple average of GFEI ratings, but also applies a relevance factor in accordance with the philosophical approach described above. Generally speaking, a top team’s games against the best opponents it faces receive more weight in the formula than its games against its weakest opposition. If it loses to weaker competition, those games receive more weight. Similarly, the opponent-adjusted offensive efficiency (OFEI) and opponent-adjusted defensive efficiency (DFEI) ratings are also a function of individual game performances and the relevance of those data points.

Collectively, I’m naming these individual game performances FEI Game Factors. Let’s take a closer look at Alabama’s FEI Game Factor profile to understand where the Crimson Tide’s No. 1 overall FEI rating is coming from.

FEI Game Factors - Alabama Crimson Tide
Team Wk Opponent Final NG Final GFEI Rk OFEI Rk DFEI Rk GW
Alabama 1 Virginia Tech W 35-10 W 35-10 .655 4 1.922 19 -.413 150 .194
Alabama 3 Texas A&M W 49-42 W 49-42 .570 16 1.710 37 -.220 211 .196
Alabama 4 Colorado State W 31-6 W 24-6 .169 261 .025 545 -.369 161 .113
Alabama 5 Mississippi W 25-0 W 25-0 .643 5 1.118 135 -1.564 5 .188
Alabama 6 Georgia State W 45-3 W 38-3 .244 199 .742 257 .239 390 .044
Alabama 7 Kentucky W 48-7 W 34-7 .360 104 .057 536 -.525 119 .089
Alabama 8 Arkansas W 52-0 W 35-0 .431 61 1.222 105 -.420 149 .074
Alabama 9 Tennessee W 45-10 W 42-3 .591 13 1.534 62 -.525 120 .102

Alabama has played eight FBS games to date and five of those games rank among the top-20 nationally in GFEI. More than half of their overall game performances rank in the 98th percentile. The relevance distribution highlights how much more important the wins over Virginia Tech and Texas A&M are to Alabama’s rating (nearly 20 percent each), and how little importance is given to the win over Georgia State (only 4.4 percent). That game is the least relevant result of the season for any team according to FEI Game Factors.

Alabama has only allowed 26 points since their shootout victory over Texas A&M, and only 19 of those points were allowed in non-garbage time. That’s dominant, but when we adjust for the strength of the opponent faced in those games, only the shutout of Ole Miss ranks among the top 100 DFEI single-game performances. It seems odd that the best Alabama offensive performance according to OFEI was the opening weekend win over Virginia Tech, a game where the Crimson Tide only scored two offensive touchdowns -- both on a short field. But the Hokies have the nation’s No. 1 defense according to FEI, and success of any kind against that unit rates favorably.

A highly-ranked offensive performance does not necessarily indicate a poor defensive performance. In the same game, Virginia Tech posted the 11th best DFEI of the season, one of five DFEI performances by the Hokies ranked among 35 best of the season (96 percentile).

FEI Game Factors - Virginia Tech Hokies
Team Wk Opponent Final NG Final GFEI Rk OFEI Rk DFEI Rk GW
Virginia Tech 1 Alabama L 10-35 L 10-35 .380 92 .820 232 -1.181 11 .136
Virginia Tech 3 East Carolina W 15-10 W 15-10 .403 77 .883 202 -.998 29 .153
Virginia Tech 4 Marshall W 29-21 W 29-21 .102 328 -.156 615 -.790 58 .126
Virginia Tech 5 Georgia Tech W 17-10 W 17-10 .505 28 .585 311 -1.170 13 .165
Virginia Tech 6 North Carolina W 27-17 W 27-10 .221 215 .259 448 -.946 35 .124
Virginia Tech 7 Pittsburgh W 19-9 W 19-9 .138 285 .396 377 -.545 113 .122
Virginia Tech 9 Duke L 10-13 L 10-13 .198 231 -.505 729 -1.626 3 .175

These tables are the guts of the FEI ratings. Why does this team rank so high? Why does that team rank so low? The answers are found in the Game Factors, all of which I’ve published on my site and will update weekly for the remainder of the year.

The weekly updates are of particular importance. Game Splits, the offense, defense, special teams, field position and turnovers splits that are recorded in each game are not opponent-adjusted, and therefore do not change when new data is collected. The Game Factors, however, will change each week. If Texas A&M keeps rising in the FEI ratings, Alabama’s GFEI value and the weight of that result will change.

Florida State’s blowout victory over Clemson ranks as the best GFEI performance of the season to date. And that’s with Clemson ranked all the way down at No. 42 in the FEI ratings. If the Tigers finish strong and climb in the FEI ratings, Florida State’s GFEI performance in that game will look more and more impressive (and the Seminoles overall rating will be impacted as a result).

FEI Game Factors - Florida State Seminoles
Team Wk Opponent Final NG Final GFEI Rk OFEI Rk DFEI Rk GW
Florida State 1 Pittsburgh W 41-13 W 41-13 .680 3 1.829 25 -.071 259 .211
Florida State 3 Nevada W 62-7 W 45-7 .196 233 .154 498 -.626 91 .113
Florida State 5 Boston College W 48-34 W 48-34 .107 320 .842 220 .698 592 .160
Florida State 6 Maryland W 63-0 W 42-0 .384 89 1.938 18 -.226 207 .140
Florida State 8 Clemson W 51-14 W 41-7 .763 1 1.685 40 -.890 45 .243
Florida State 9 North Carolina State W 49-17 W 42-10 .049 372 .619 300 .070 310 .133

Even without dramatic changes in the ratings of opponents, the relative weight of each game will shift over time. Florida State’s win over Clemson is the most impressive game of the season, and it carries nearly 25 percent of the weight of the Seminoles FEI rating. Louisville’s loss to Central Florida carries nearly 25 percent of the weight for the Cardinals. Baylor’s win over Kansas State is similarly weighted. Individual Game Factors on average account for about 14 to 15 percent of each team's rating. As each team plays more games, the relative weight of past games will decrease simply due to the influx of more data.

Click here for the FEI Game Factors for all 125 FBS teams

I’m sure there will be many surprises in the FEI Game Factors data tables. There may be more questions raised than answered in the tables as well. Let me know.

FEI Week 9 Top 25

The Fremeau Efficiency Index (FEI) rewards playing well against good teams, win or lose, and punishes losing to poor teams more harshly than it rewards defeating poor teams. FEI is drive-based and it is specifically engineered to measure the college game. FEI is the opponent-adjusted value of Game Efficiency (GE), a measurement of the success rate of a team scoring and preventing opponent scoring throughout the non-garbage-time possessions of a game. FEI represents a team's efficiency value over average.

Other definitions:

  • SOS Pvs: Strength of schedule based on the likelihood of an elite team going undefeated against the given team's schedule to date.
  • SOS Fut: Strength of schedule based on the likelihood of an elite team going undefeated against the given team's remaining schedule.
  • FBS MW: Mean Wins, the average number of games a team with the given FEI rating would be expected to win against its entire schedule.
  • FBS RMW: Remaining Mean Wins, the average number of games a team with the given FEI rating would be expected to win against its remaining schedule.
  • OFEI: Offensive FEI, the opponent-adjusted efficiency of the given team's offense.
  • DFEI: Defensive FEI, the opponent-adjusted efficiency of the given team's defense.
  • STE: Special Teams Efficiency, the composite efficiency of the given team's special teams units - field goals, punt returns, kickoff returns, punts, and kickoffs.
  • FPA: Field Position Advantage, the share of the value of total starting field position earned by each team against its opponents.

These FEI ratings are a function of results of games played through October 26th. The ratings for all FBS teams can be found here. Program FEI (five-year weighted) ratings and other supplemental drive-based data can be found here.

Rk Team FBS
Rec
FEI LW GE GE
Rk
SOS
Pvs
Rk SOS
Fut
Rk FBS
MW
FBS
RMW
OFEI Rk DFEI Rk STE Rk FPA Rk
1 Alabama 8-0 .322 1 .405 4 .320 43 .410 28 9.7 2.4 .461 18 -.672 6 7.219 1 .624 1
2 Stanford 7-1 .291 2 .194 10 .212 18 .320 18 9.8 3.1 .282 31 -.779 2 5.046 2 .591 2
3 Oregon 7-0 .288 4 .418 3 .546 86 .173 3 9.2 2.7 .614 9 -.541 9 1.008 42 .553 12
4 Florida State 6-0 .267 5 .448 2 .704 103 .575 51 10.0 4.4 .471 15 -.485 12 -.343 72 .544 18
5 Missouri 6-1 .263 3 .178 13 .340 49 .482 39 9.2 3.3 .310 28 -.624 7 -1.120 91 .545 17
6 BYU 6-2 .253 10 .113 32 .289 36 .517 43 8.8 2.3 .137 46 -.747 4 -.188 67 .524 37
7 Baylor 6-0 .245 8 .479 1 .763 110 .411 29 9.6 3.9 .634 7 -.327 26 -1.886 102 .532 29
8 LSU 6-2 .228 9 .176 15 .240 23 .233 4 8.0 1.8 .737 3 -.107 49 1.852 25 .523 39
9 Utah 3-4 .223 6 -.029 70 .092 5 .295 15 6.9 2.7 .480 14 -.286 30 1.638 31 .490 73
10 South Carolina 6-2 .222 19 .096 37 .181 14 .832 89 8.6 2.6 .614 8 -.419 18 -3.277 117 .454 111
11 Miami 6-0 .217 7 .208 9 .651 98 .238 5 8.5 3.2 .485 13 -.374 23 .622 47 .540 22
12 Arizona State 4-2 .217 11 .108 35 .188 16 .291 14 7.4 3.3 .704 4 -.476 13 -.590 82 .523 40
Rk Team FBS
Rec
FEI LW GE GE
Rk
SOS
Pvs
Rk SOS
Fut
Rk FBS
MW
FBS
RMW
OFEI Rk DFEI Rk STE Rk FPA Rk
13 Ohio State 7-0 .213 22 .292 6 .719 105 .714 70 9.9 3.5 .643 6 -.191 38 3.961 4 .555 10
14 Auburn 6-1 .210 15 .108 33 .263 27 .357 23 8.1 2.8 .277 32 -.535 10 1.670 29 .505 59
15 Texas A&M 5-2 .208 16 .147 20 .218 19 .274 10 7.7 2.5 .907 1 .292 101 2.846 10 .565 7
16 Virginia Tech 5-2 .203 18 .032 58 .155 11 .540 45 7.8 3.1 -.055 66 -1.091 1 -2.362 112 .500 67
17 Georgia 4-3 .202 12 .019 60 .263 28 .355 21 7.3 2.6 .678 5 -.167 40 .284 56 .463 102
18 Central Florida 6-1 .192 13 .266 7 .458 66 .816 86 10.2 4.6 .528 10 -.152 42 2.904 9 .547 16
19 Mississippi 4-3 .190 14 .040 54 .070 2 .584 52 6.9 3.1 .324 27 -.457 16 -.141 66 .477 87
20 USC 5-3 .185 27 .063 49 .240 24 .325 19 9.1 3.5 .210 37 -.747 3 .027 61 .542 21
21 Oklahoma State 5-1 .174 25 .138 24 .804 118 .356 22 8.2 3.2 .215 35 -.463 15 -.834 86 .554 11
22 Georgia Tech 4-3 .171 28 .058 51 .155 10 .630 60 6.0 2.0 .287 30 -.257 33 2.124 20 .501 64
23 Oregon State 6-1 .171 20 .170 16 .301 39 .170 2 6.9 1.6 .288 29 -.283 31 .419 52 .548 14
24 Louisville 6-1 .166 24 .373 5 .730 106 .825 87 9.7 3.4 .419 19 -.304 27 1.330 39 .523 41
25 Arizona 4-2 .160 23 .147 21 .339 48 .289 13 7.2 3.1 .464 17 -.381 21 -1.590 99 .506 57

Posted by: Brian Fremeau on 30 Oct 2013

7 comments, Last at 16 Jan 2014, 1:53am by jordan espa

Comments

1
by Kal :: Wed, 10/30/2013 - 6:03pm

I know I always ask about this, so apologies - where do special team scores factor into the GFEI and weighings?

3
by Brian Fremeau :: Wed, 10/30/2013 - 9:49pm

Special teams are incorporated in the ratings in that they are part of the raw game efficiency data that is then adjusted to produce GFEI.

5
by Kal :: Thu, 10/31/2013 - 3:31pm

Good to know. Thanks!

2
by Kal :: Wed, 10/30/2013 - 6:18pm

Also since I"m thinking about it - it seems like GFEI and GW are a really great way to account for some serious injuries or disruptions in a team in a nice, organic (albeit manual) way. For example, you can reduce the weight of Georgia's good scores against Clemson as an indication that it isn't likely going to happen again due to the injuries. Last season you could deprioritize Stanford's results without Kevin Hogan and reweigh based on more current results.

Have you given any thought to doing these kinds of tweaks? Dealing with injuries is one of the big holy grail of advanced stat analysis, and it's pretty exciting to see a system that may be able to handle it almost effortlessly.

4
by Brian Fremeau :: Wed, 10/30/2013 - 9:57pm

I have given some thought to modifying the weights of the data in a number of ways, and certainly participation and injury data could be applied here. More recent results could also receive more weight.

6
by Tai (not verified) :: Tue, 11/05/2013 - 8:22pm

Good snap count data for college (like this site offers for the NFL) would be wonderfully helpful in building a good adjustment model to properly weight games earlier in the season, while ultimately trying to assess the current strength of active rosters. That data could also be a great tool for more accurate preseason ratings in many models that currently look at returning starters; I think you'd get a much better picture if you could look at the percentage of prior-year snaps returning.

None of this has much to do with FEI, but this comment made me think about it. Snap counts are a stat I've been fantasizing about having access to for college analysis since before they were even available for the NFL. I know they probably won't show up any time too soon, data collection would be a massive project if they were going to be comprehensive. Still, it would be so great...

7
by jordan espa (not verified) :: Thu, 01/16/2014 - 1:53am

Howdy just wanted to give you a quick heads up. The words in your post seem to be running off the screen in Opera. I'm not sure if this is a formatting issue or something to do with internet browser compatibility but I thought I'd post to let you know. The layout look great though! Hope you get the problem solved soon. Kudos
jordan espa