sportsbetting moneyline rookie question

[awieise]

Suppose I have found a system that historically produces straight-up winners 81% of the time. Assume adequate sample size.

Suppose there are 10 games on tonight's card that fit this system.

Suppose I bet $100 on each of the ten games. They are all favorites, naturally, so I end up risking $1000 to win $290 (29%). These are the actual moneylines for these games.

Since my system produces winners 81% of the time, it produces losers 19% of the time.

Since 29% (percent profit if I win) is greater that 19% (risk of loss), this system/betting procedure stands to win 10% ROI over the long haul.

Is the above conclusion correct, or am I missing something?? Please explain. Thank you.

[Kerth]

On a $100 bet, 81% of the time you'll make a profit of $29 and 19% of the time you'll lose the $100. The EV of the bet is then:

0.81 * $29 - 0.19 * $100 = $4.49

ROI = 4.49%

[awieise]

thank you!

[Padre]

I have always thought that u find out what the % of that ten teamer of hitting are, or losing?

U say that u hit 81% of games.

That would not directly translate into 81% of the 10 team parlays.

i think that would be .81 to the power of 10. right?


So u would only hit 12.15% of those parlays.

now i would figure that 12.15 * $29= $352.00
minus the 87.85 * 100= -$8785

For a disturbing loss of $8433 or a Negative 843.3% ROI

But i can either be way off or not understand the orginal %'s. But i would also like help with this, because i too look for trends or systems in baseball, and use the above logic in determining when it is a postive EV in order for me to use it.

I may have did it wrong and firgured it to win and not lose, rather than to lose and not win, ex: .19 to the 10th power.? not sure