So, how does that translate to long term profit? That requires some simple math. In a two event parlay there are four possible combinations – you win both games, you lose both games, you win the first and lose the second, and you lose the first and win the second. If the point spreads are set reasonably well then in each game there should be about an even chance of ending up on either side of the spread. That means that the likelihood of each one of those four possible outcomes is basically the same – 25 percent. That in turn means that in order for you to break even betting any one of those combinations over the long term you would need odds of 3/1 – and better than that to show a profit. Since two teams parlays typically pay off at about 2.6/1 parlays are typically not a great bet because of their negative expectation – you are losing money in the long term even when you win a parlay bet. When two events are correlated, though, then the percentages change. Let’s say that in our original example the chances of winding up on either side of the 30 point spread is the same. If the favorite covers, though, then it is going to go over the total much more often than it goes under – because the favorite has to cover at least 31 points to cover, so there aren’t that many scores that will allow the favorite to cover and the game to still go under the total. We could say, then, that if the favorite covers there is an 80 percent chance that the game will go over, and a 20 percent chance that it will go over. Overall, then, that means that there is a 40 percent chance that the game will go over and the favorite will cover. That means that 40 percent of the time you parlay the favorite and the over you are going to win. If you made a $100 parlay bet 10 times then you would expect to win four times with a total profit on those wins of $1040. The six losses would cost you a total of $600. That means your profit would be $440.
Interesting i've never thought about this in depth l0l