Mathematics and Betting Thread

[arbboy]

The thing is though that a "perfect" arb bet should be a perfect bet to keep.  Arbing is just a tool to reduce variance that comes at a cost.

The solution might be to have a process for time pressure situations eg look at the correct score market for the TV high liquid matches.  Or even just do a shout out in the thread for bets at 10s+ same price in liquid betfair markets.

The perfect arb bet is to back a 5/1 shot at 11/2 and lay it at 9/2.  ie both bets individually are both value.  With regard to my 100/1 'first scoring play in the superbowl' i backed 100/1 and laid it at 55/1 on bf with 2 of the £25 free bets i had.  I have no idea whether the 100/1 is value or laying 55/1 on bf is value.  I would imagine both trades are value trades and i can make them both without any risk to myself and no swings to worry about.  I would imagine the correct price is somewhere between the two and at the same time convert a £25 free bet into actual cash with a profit on top with no risk at all.

[doubleup]

point taken but usually the error is on one side and in the context of this discussion we are usually looking for a bet that is as close to ev neutral as possible.

[BorntoBubble]

Coral had a mobile offer today of 2/1 for hazard or oscar to score anytime.

The best prices were 5/1 and 4/1 I think. So if i just backed them at the best prices I get

£8 on at 4/1 and
£10 on at 5/1
I win £40 if either score and £80 if both score.

Yet if i place £18 with coral i get £36? Have I got the maths right here and this is a shocking offer? Or is there something im missing.

If the odds of two individual events are priced at 5/1 and 4/1 what is the calculation for working out either or happening is that using that nCr calculation? I probably should know this but my brain is doing a brain fart.

Why if these calculations are correct to bookies send out these offers if they are horrific?

[rfgqqabc]

Coral had a mobile offer today of 2/1 for hazard or oscar to score anytime.

The best prices were 5/1 and 4/1 I think. So if i just backed them at the best prices I get

£8 on at 4/1 and
£10 on at 5/1
I win £40 if either score and £80 if both score.

Yet if i place £18 with coral i get £36? Have I got the maths right here and this is a shocking offer? Or is there something im missing.

If the odds of two individual events are priced at 5/1 and 4/1 what is the calculation for working out either or happening is that using that nCr calculation? I probably should know this but my brain is doing a brain fart.

Why if these calculations are correct to bookies send out these offers if they are horrific?

The word boost gets people excited. Lol maffs etc.

[BorntoBubble]

Coral had a mobile offer today of 2/1 for hazard or oscar to score anytime.

The best prices were 5/1 and 4/1 I think. So if i just backed them at the best prices I get

£8 on at 4/1 and
£10 on at 5/1
I win £40 if either score and £80 if both score.

Yet if i place £18 with coral i get £36? Have I got the maths right here and this is a shocking offer? Or is there something im missing.

If the odds of two individual events are priced at 5/1 and 4/1 what is the calculation for working out either or happening is that using that nCr calculation? I probably should know this but my brain is doing a brain fart.

Why if these calculations are correct to bookies send out these offers if they are horrific?

The word boost gets people excited. Lol maffs etc.

Just it was so bad (using my maths) I assumed i got it wrong.

Sad that im sat here looking at maths on betting rather than getting a maths degree.

[Tal]

You mean £8 at 5/1 and £10 at 4/1, right?

[BorntoBubble]

You mean £8 at 5/1 and £10 at 4/1, right?

Yeah i did!

[doubleup]

with this kind of bet just work out how much you need to bet to return £100 on both bets so £20 @ 4-1 gives you a £100 return and £16.67 @ 5-1 gives you a £100 return.

If you add them together you get £36.67 bet will get you £100 return if either of them win -- in comparison to £33.33 bet @ the 2-1 getting you same £100 if either win.

So the 2-1 is better as you only lose £33.33 if the bet fails and you get the same return if it wins.

[doubleup]

oops misread your problem - obv a bad offer as you can get the double payout

[doubleup]

ok having another look at it with fresh eyes, think I have it now....


Your method is wrong because I win £40 if either score isn't correct as you haven't deducted the loss from the other bet.

ie when you win the £8 at 5-1, you lose the £10 at 4-1, so you actually just win £30.

Back to my above post comparing the returns


you get £36.67 bet will get you £100 return if either of them win with the two separate bets  in comparison to £33.33 bet @ the 2-1 getting you same £100.


I had a mess around with a Poisson calculator (assuming that the 5-1 and 4-1 odds are accurate) to try and find an approximate % where both players score and it seems to be about 3% or so

So if we say roughly 66% neither scores, 31% either player scores and 3% both score

For our stake of £36.67 we get

nil 66%

£100 31% = £31

£200 3% = £6

So a return of £37

If we put the same £36.67 on the offer @ 2-1 our return would be

£110 34% = £37.40


So after all that really not much in it.

[JaffaCake]

I am gonna reread this thread but if it hasn't been covered, this is what I posted on TfT:

"Red/Argue....how do u decide what's bes, 10/11 at one total or evens at a point higher or whatever. Is there proper maths behind it or is it a feel thing? Same for if say we can back a horse at 16/1 ew with 4 places or 14/1 ew with 5 places (or whatever).

Is that a question best asked on the maths thread?"

Also wanted to add, quite often I look at basketball handicaps, one firm will be 10/11 +6.5, another evens +7, another 8/11 +10 etc etc

[arbboy]

Stu is def your man for the maths side of buying points etc in nba. 

[redarmi]

Posted this in TFT:

"The NBA are fairly easy to work out.  Each individual point is likely to land a certain amount of time so has a value.  In the NBA for a regular pointspread most half points are worth about 0.05 in decimals.  So-3 2.0 is about the same as -3.5 2.05.  They differ slightly as some pointspreads are more likely to fall and I have charts for them but as a rule 0.05 is fine.

As for horseracing places - feel is better.  There is some very heavy academic work on how likely a horse is to place and nobody has "solved" it as such but if you look at enough of them you get a reasonably good feel.  An okay rule of thumb is if you turn the prices into percentages so in the case you said.  The place price at 14/1 is 7/2 (14/4) or 22.22% for 5 places.  For 4 places it is 4/1 (16/4) or 20%so they are effectively they are saying there is a 2.22% chance of your horse coming 5th (22.22%-20%) which is about a 45/1 shot so ask yourself would I back this horse to come fifth at 45/1?  That sounds like value to me so I would take the extra place and even if I only thought it was fair value I would take it because the extra place reduces my variance.  Does that make sense?"

I didn't actually address your question on nba totals though.  It is probably about 0.04 for NBA totals as a rule.  If you have a pinnacle account then log into your account and look to see what they charge and they are pretty much spot on.  If you find a book offering much different to what pinnacle offer then that book is wrong and you have a bet.  If you want the NBA pointspreads I have a chart I did one time but I don't think I ever did the totals because they don't vary as much so 0.03-0.04 works well.

[Longines]

I've been thinking about this spread betting question and it's making my head hurt, wonder if anyone can help.

On average, 0.22 penalties are scored in each champions league game so if it was a normal bet then in theory we fill our boots when offered 5/1 or better on a penalty being scored.

Assuming the time that the penalties are scored is random and evenly spread throughout the 90 minutes* how do you determine the buy or sell point at which a bet is strictly mathematically +EV?


*big assumption, I know.

[doubleup]

4-1 or better surely

[/nitmanship]


edit

although it occurs to me that some matches have more than one penalty, so really the relevant stat is the % of matches with penalties