2021 Week 3 Bayesian Power Rating

Recently we posted our first Strength power rating, and as expected after just 3 weeks (and for most teams, only two FBS opponents), there were a lot of odd results.

Our Bayesian updates to our pre-season ratings are a lot more reliable at this point—even though it's partly based on last year's weird season—but we will compare them with the Strength power rating to see where they agree.

First, the big upward movers:

• Wyoming, up 20 to #36 for beating Ball State 45-12
• USC, up 19 to #39 after beating Washington State 45-14
• Michigan State, up 16 to #56 after winning at Miami 38-17
• Washington, up 13 to #57 after beating Arkansas State 52-3
• Georgia Tech, up 13 to #78 after almost upsetting Clemson, losing 14-8

Now let's compare lists. #1 is still Alabama; they are only #14 in the early Strength ranking. Iowa has made it all the way to #2 below, and is #10 in Strength. Oklahoma slips to #3 and is #18 in Strength. Georgia is almost a match: #4 in Bayesian and #2 in Strength!

So far what we can see going on is that our initial ranking has had an effect. The top four teams are objectively playing well—all top 20—but our prior knowledge of these teams has put them closer to where they "should" be. In other words, Strength can tell these teams are pretty good, but can't conclude that they are top level.

And there are outliers. #5 below is Wisconsin, and they are just #53 in Strength. Partly that's because they've played just two games, and also, maybe we overrated Wisconsin in our pre-season rankings. Penn State beat Wisconsin but is behind them at #6—mostly because they started at #22 and have been working their way up. They're #28 in Strength, not very good but well above Wisconsin there.

#7 Iowa State is at #24, #8 Clemson is #20, #9 Cincinnati is #16, and #10 Mississippi is #3 in Strength. So there is some correspondence, but generally 10-20 places difference. The reality probably lies somewhere in between the two rankings.

The top teams in Strength are Michigan, Georgia, Mississippi, Washington, and North Carolina. Michigan has made it up to #14 in our Bayesian ranking, so the Wolverines look legit though #1 might be quite a stretch. #2 Georgia is #4 in Bayesian and #2 in the AP poll and many other power ratings like ESPN's FPI, so that one looks accurate for both ratings. Mississippi is #10 below, and #13 in the AP so they could be a legit top ten team.

Washington's #4 rating in Strength stems from their weird season so far, which includes a huge loss to Michigan and a 49 point win over Arkansas State. It's a great example of how a small sample can make things go awry. The power rating basically "decided" that Michigan is so great that Washington's loss to them doesn't hurt the Huskies. They did move up a lot in our Bayesian rating but they're only #57. It's probably very safe to say Washington is somewhere between #4 and #57. Not very helpful, but it's hard to be accurate this early for a team with such an erratic start.

North Carolina ranks 5th in Strength and #11 below, so that's a pretty tight range. They already lost to Virginia Tech but both power ratings are saying that might have been a fluke. And since the Hokies rank #6 in Strength, it doesn't need to be much of a fluke there, but they're only #47 below, so the jury is definitely out.

Each passing week should bring the two systems closer together, until we abandon the Bayesian system altogether in about a month.

2021 Bayesian power rating update for week 3

W2	W3	Team	W3 Rating
1	1	Alabama	28.88
3	2	Iowa	27.68
2	3	Oklahoma	25.66
4	4	Georgia	24.13
6	5	Wisconsin	23.30
7	6	Penn State	20.96
9	7	Iowa St	20.86
5	8	Clemson	20.66
16	9	Cincinnati	19.15
19	10	Mississippi	18.61
14	11	North Carolina	18.26
12	12	Ohio State	18.06
10	13	Texas A&M	18.03
20	14	Michigan	17.76
8	15	Arizona St	17.51
17	16	Auburn	16.86
23	17	Minnesota	15.34
26	18	Texas	15.31
18	19	Indiana	13.76
15	20	UCLA	13.56
13	21	Miami FL	12.94
22	22	Notre Dame	12.82
21	23	Arkansas	12.81
11	24	Toledo	12.47
32	25	Brigham Young	11.62
24	26	Coastal Carolina	11.58
37	27	Florida	10.89
30	28	Western Michigan	10.59
38	29	Nebraska	10.40
27	30	Rutgers	10.39
29	31	Kent St	10.31
39	32	Louisiana-Lafayette	10.29
31	33	TCU	10.13
46	34	LSU	9.40
35	35	Oklahoma St	9.28
56	36	Wyoming	8.78
34	37	Maryland	8.30
25	38	Central Michigan	7.75
58	39	Southern Cal	7.33
42	40	Wake Forest	6.77
28	41	Ball St	6.29
49	42	Baylor	6.13
48	43	North Carolina St	5.89
44	44	Boise St	5.72
50	45	West Virginia	5.43
36	46	Miami OH	5.42
45	47	Virginia Tech	5.27
33	48	Eastern Michigan	5.07
40	49	Oregon	5.06
41	50	Appalachian St	4.91
47	51	Utah	4.81
62	52	California	4.79
52	53	Buffalo	4.79
43	54	Liberty	4.65
53	55	Pittsburgh	4.56
72	56	Michigan St	4.33
70	57	Washington	4.25
51	58	Mississippi St	4.11
55	59	Virginia	3.99
61	60	Purdue	3.33
57	61	Central Florida	2.84
63	62	San José St	1.91
54	63	Nevada	1.48
65	64	Missouri	1.27
59	65	Tulane	0.88
77	66	Kansas St	0.69
60	67	Northwestern	0.54
66	68	Troy	0.48
73	69	Oregon St	-0.89
67	70	Houston	-0.92
76	71	Louisville	-1.02
64	72	Colorado	-1.07
81	73	Tennessee	-1.28
83	74	Alabama-Birmingham	-1.29
75	75	Memphis	-1.36
71	76	Marshall	-1.68
74	77	Texas-San Antonio	-1.94
91	78	Georgia Tech	-2.07
68	79	Kentucky	-2.12
88	80	Texas Tech	-2.49
79	81	Boston College	-2.69
94	82	Fresno St	-2.82
89	83	East Carolina	-2.89
84	84	Tulsa	-3.15
86	85	Illinois	-3.17
85	86	San Diego St	-3.18
90	87	Stanford	-3.86
69	88	Northern Illinois	-4.26
80	89	SMU	-4.28
82	90	Army	-5.26
78	91	Syracuse	-5.39
93	92	Hawai`i	-5.74
92	93	Florida Atlantic	-6.34
103	94	Colorado St	-6.87
87	95	Washington St	-7.41
97	96	Florida St	-8.91
95	97	Ohio U.	-9.36
96	98	Georgia St	-9.83
100	99	South Carolina	-10.13
98	100	Air Force	-11.76
101	101	Middle Tennessee St	-12.01
104	102	South Alabama	-12.24
107	103	Utah St	-14.45
111	104	Duke	-15.44
99	105	Arkansas St	-15.59
108	106	Louisiana Tech	-15.79
102	107	Rice	-16.20
105	108	UNLV	-17.13
109	109	Vanderbilt	-18.40
106	110	Texas St-San Marcos	-18.41
113	111	Southern Miss	-18.58
112	112	Georgia Southern	-18.74
115	113	New Mexico	-18.85
118	114	South Florida	-19.54
116	115	Western Kentucky	-20.72
110	116	Arizona	-21.04
114	117	Florida Int'l	-21.26
117	118	North Texas	-24.04
119	119	UNC-Charlotte	-25.84
121	120	Bowling Green	-26.46
120	121	Akron	-28.05
123	122	Navy	-28.81
122	123	Temple	-28.82
124	124	Kansas	-29.79
126	125	Old Dominion	-30.23
125	126	UTEP	-30.83
127	127	Louisiana-Monroe	-33.83
128	128	Massachusetts	-38.61
130	129	Connecticut	-42.79
129	130	New Mexico St	-42.80