Forums

We want to share an important update with our Betfair Community users.

Over the coming months, the Betfair Community platform will be winding down. The final active day for the platform will be December 21st. From December 22nd, users will no longer be able to access the platform.

Your discussions, insights, engagement, and, most importantly, feedback have helped shape the platform and guided innovation. Your feedback continues to be important to us, and we will continue to listen via our dedicated feedback channels, as well as through product testing and innovations.

To share your feedback and experience, visit: https://support.betfair.com/app/home

General Betting

Welcome to Live View – Take the tour to learn more
Start Tour
There is currently 1 person viewing this thread.
murphyjust.
27 Mar 12 19:27
Joined:
Date Joined: 31 Jan 04
| Topic/replies: 333 | Blogger: murphyjust.'s blog
a bag has 3 balls of different colurs, one green, one blue and one orange.

I'm offered odds of 4/1 to pick out the orange ball. Obviously the true odds are 2/1. How do I express my edge mathematically?

Is it (q-p)/q*100, where q=true odds as percentage, p=odds taken as percentage?

(33-20)/33*100= 40% edge? So every £1 invested should return 1.40
Pause • Switch to Standard View question for the maths boys..
Show More
Loading...
Report Andriy • March 27, 2012 8:44 PM BST
Every £1 invested returns £1.67, so ROI (for me the same as edge) is 66.67%.

Imagine 3 goes, staking £1 each time. Probabilistically, you will win once.

Total stake = £3
Returns = £5

Profit = £2

ROI = Profit/stake = 2/3
Report ror • March 27, 2012 9:04 PM BST
Edge is your change in EV. (expected value).

Expected Value is Sum of Probability*Profit over each outcome. At 4/1 you win 4 pounds 1 in 3 times and lose 1 pound 2 in 3.

So, your EV is 4*(1/3) - 1*(2/3)=2/3 = 66.7% edge.


Probability(Win)*Profit - Probability(Loss)*Stake.

Or if you prefer, you can do Probability(Win)*Return - Stake.
Report dunlaying • March 28, 2012 11:46 AM BST
Let F=fair odds
Let P=payoff odds
House advantage
F-P/[1+F]
Punter advantage
P-F/[1+F]
So in your example
4-2/[1+2]=2/3=67%
Report JLivermore • March 28, 2012 12:34 PM BST
one more answer can't hurt.

To put it in your language:

(q-p/p)*100

=(0.13/0.2)*100  = 67%

you just got the choice of divisor wrong
Report murphyjust. • March 29, 2012 5:28 PM BST
thanks all - knew i was wrong but couldn't see wood from trees..
Post Your Reply
<CTRL+Enter> to submit
Please login to post a reply.

Wonder

Instance ID: 13539
www.betfair.com