Mathematics Of Football Upsets

Almighty Colin · 11-14-2002

This is pretty interesting if you follow the point spreads or participate in the pools. The chances of an upset in a game fall exponentially as the point spread increases.

Here is a table that demonstrates the likelihood of an upset.

Points Upset%
1 47%
2 44%
3 42%
4 39%
5 35%
6 33%
7 31%
8 28%
9 26%
10 24%
11 21%
12 19%
13 18%
14 16%
21 6.7%
28 2.3%

A 7 point underdog wins 31% of the time.
A 14 point underdog wins 16% of the time.
A 21 point underdog wins 6.7% of the time.
A 28 point undersog wins 2.3% of the time.

You can see the effect of doubling the spread from 7 to 14 decreases by about 1/2 the chance of an upset. It decreases by about another 1/2 when the spread goes from 14 to 21.

Vick · 11-14-2002

Colin is this mathematical probability or done on statistical data from actual NFL games?
Is the win including the point spread or is in the outcome of the game without the point spread?

Almighty Colin · 11-14-2002

Vick -

I thought you'd be the first to post in this thread.

Probabilty AND data. There are white papers that show the error on NFL point spreads is calculated from the standard deviation for football games (14 points) using the bell-curve. The table I displayed is from theory but is very close to the real data.

The win is not including the point spread. In other words, since the Cardinals are 11 point underdogs to the Eagles this weekend, there is about a 21% chance they will win the game outright.

More accurately, 11 point underdogs win 21% of the time.

Since the error is distibuted symetrically - there is also a 21% chance that an 11 point favorite will win by 22 points.

Last edited by Colin at Nov 14 2002, 10:48 AM

JerryW · 11-14-2002

One thought on this is that when picking the spreads, the handicappers are not trying to pick the probability of the winning spread, but rather to insure that equal amounts are bet on each side of the proposition. They do not want to pay the winners from their pockets, but rather the loosers pockets. This will tend to skew the results somewhat from the mathematical curve.

Almighty Colin · 11-14-2002

Jerry,

It still works out that the error distribution is "normal" because the attempts to equalize the betting on each side of the spread refects the knowledge of the "smart money". What it means is that there is a 67% chance that a game will be within 14 points of the line. Well, that's sort of a lot but the interesting thing is it is symmetrical about the spread. It's still the best bet.

The same thing happens when one used a mathematical betting system. such as Massey ratings - see http://www.mratings.com

The errors are distributed normally because the error in the predictions is reflective of imperfect knowledge and chance with an equal amount on each side of a bet. If enough people catch on to a new idea that is a better predictor than the spread, the spread will move to reflect it.

11-14-2002	#1
Almighty Colin Members Want to see your own Advertising Here! Join Date: Oct 2002 Posts: 8,059	This is pretty interesting if you follow the point spreads or participate in the pools. The chances of an upset in a game fall exponentially as the point spread increases. Here is a table that demonstrates the likelihood of an upset. Points Upset% 1 47% 2 44% 3 42% 4 39% 5 35% 6 33% 7 31% 8 28% 9 26% 10 24% 11 21% 12 19% 13 18% 14 16% 21 6.7% 28 2.3% A 7 point underdog wins 31% of the time. A 14 point underdog wins 16% of the time. A 21 point underdog wins 6.7% of the time. A 28 point undersog wins 2.3% of the time. You can see the effect of doubling the spread from 7 to 14 decreases by about 1/2 the chance of an upset. It decreases by about another 1/2 when the spread goes from 14 to 21. __________________ Almighty Content. Your one stop for live content. Secret Friends, LATINA Secret Friends , My Cam Friends

11-14-2002	#2
Vick Celebrating Company's Success with A Beer From Mini Bar Want to see your own Advertising Here! Join Date: Oct 2002 Location: Little South of Sanity Posts: 6,551	Colin is this mathematical probability or done on statistical data from actual NFL games? Is the win including the point spread or is in the outcome of the game without the point spread? __________________ Pssst Click the Button Above I once wanted to be a Gynecologist But I couldn't find an opening

11-14-2002	#3
Almighty Colin Members Want to see your own Advertising Here! Join Date: Oct 2002 Posts: 8,059	Vick - I thought you'd be the first to post in this thread. Probabilty AND data. There are white papers that show the error on NFL point spreads is calculated from the standard deviation for football games (14 points) using the bell-curve. The table I displayed is from theory but is very close to the real data. The win is not including the point spread. In other words, since the Cardinals are 11 point underdogs to the Eagles this weekend, there is about a 21% chance they will win the game outright. More accurately, 11 point underdogs win 21% of the time. Since the error is distibuted symetrically - there is also a 21% chance that an 11 point favorite will win by 22 points. Last edited by Colin at Nov 14 2002, 10:48 AM __________________ Almighty Content. Your one stop for live content. Secret Friends, LATINA Secret Friends , My Cam Friends

11-14-2002	#4
JerryW Members Join Date: Oct 2002 Location: Spain Posts: 146	One thought on this is that when picking the spreads, the handicappers are not trying to pick the probability of the winning spread, but rather to insure that equal amounts are bet on each side of the proposition. They do not want to pay the winners from their pockets, but rather the loosers pockets. This will tend to skew the results somewhat from the mathematical curve. __________________ Programer available: C/C++/C#, PHP and MYSQL, Windows and Unix. Experience with video, photos, web site development, custom browsers and data collectors, games, etc. ICQ 321 950 261 Email: webmaster @ rgt4.com

11-14-2002	#5
Almighty Colin Members Want to see your own Advertising Here! Join Date: Oct 2002 Posts: 8,059	Jerry, It still works out that the error distribution is "normal" because the attempts to equalize the betting on each side of the spread refects the knowledge of the "smart money". What it means is that there is a 67% chance that a game will be within 14 points of the line. Well, that's sort of a lot but the interesting thing is it is symmetrical about the spread. It's still the best bet. The same thing happens when one used a mathematical betting system. such as Massey ratings - see http://www.mratings.com The errors are distributed normally because the error in the predictions is reflective of imperfect knowledge and chance with an equal amount on each side of a bet. If enough people catch on to a new idea that is a better predictor than the spread, the spread will move to reflect it. __________________ Almighty Content. Your one stop for live content. Secret Friends, LATINA Secret Friends , My Cam Friends