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# Rob Gillespie Gaming Guru

### The Mathematics of Moneylines

12 November 2002

By Rob Gillespie
by Rob Gillespie

Last week we talked about which is more important, hitting or pitching, when picking winners in baseball. Based on the your email responses, it seems most of you prefer the pitching route. This week I want to discuss moneylines in baseball and how the mathematics involved should impact your wagering decision.

Let's start with a question. Which of these bets would you prefer to place?

a) \$300 to win \$100 on a heavy favorite with a 75% chance of winning

b) \$150 to win \$100 on a medium favorite with a 60% chance of winning

c) \$100 to win \$200 on an underdog with a 33.33% chance of winning

This is a trick question; the correct answer is that each scenario is essentially the same with an expected return of \$0.

In scenario 'a', 75% of the time you win \$100, but you lose \$300 the other 25%.

Expected return = (.75 * 100) - (.25 * 300) = 75 - 75 = 0

In scenario 'b', 60% of the time you win \$100 but you lose \$150 the other 40%.

Expected return = (.60 * 100) - (.40 * 150) = 60 - 60 = 0

In scenario 'c', 33.33% of the time you win \$200 but you lose \$100 the other 66.66%.

Expected return = (.3333 * 200) - (.6666 * 100) = 66.66 - 66.66 = 0

I think you can see the pattern here. To calculate the percentage of wins required to break-even for any moneyline, use the following formula:

Required Win % = Amount Risked / (Amount Risked + Amount of Win)

e.g..: a line of -110 implies a risk of \$110 to win \$100 so….

Required win % = 110 / (110 + 100) = 110/210 = 52.38% (Loyal readers will have seen this number before in my column!)

I can hear the collective groan from here as you remember why you hated high school algebra, but I implore you to spend a few minutes on this if you want to be profitable at baseball or any other sport. If you like, you can email me at rob@bodog.com and I can send you my chart that covers +300 dogs to -320 favorites.

"Why is this important?" you ask. Simple. Every time you look at a moneyline, you need to know what winning % you need to break even. If you expect the -300 favorite from scenario a to win 80% of the time, than you've got a betting opportunity. If you expect a win only 70% of the time, than you should pass and move on to analyzing the next game.

I notice that most handicappers prefer to play underdogs and small favorites, while public bettors like the big favorites. Which is better? It depends on the game. Handicappers like underdogs and small favorites because these are picks that are harder for the average player to come up with. If you called a betting service and were told "I really like the Diamondbacks with Randy Johnson on the hill hosting the Brewers tonight", would you be happy that you had just played \$10 or \$20 or \$50 for that pick? No way! Randy Johnson and the D-Backs should beat the Brewers every time out. If you are paying for a pick, you want something a little less obvious.

Another reason handicappers prefer betting the dog is it eliminates big losses. If Randy has an off night and the Brewers get the upset win over a -320 favorite, would you call that handicapping service again? Probably not. But if the same handicapper hits a win with a +160 dog, you would be impressed, and would be far more likely to use the service again. The handicappers aren't being dishonest in any way, it's just the nature of their business.

Although handicappers shy away from big favorites, you don't have to. Looking through the first four weeks of the baseball season, I see 17 games have closed with prices on the favorite of -250 or higher (including the Yankees eight times, and D-Backs six). 15 of these games have been winners against just 2 losers. Placing a bet to win \$100 each time would have returned \$970 on \$4530 in risk for a return of 21.4%! We have one player at BoDog who has placed much bigger amounts on almost all of these games and he has been sent some big checks this month!

Remember that it doesn't matter how big the price or how much you get back - as long as you know where the break-even point is. Keep this in mind the next time someone says "I never lay more than 140 on a baseball game." You can now tell them when they should.

As promised, I also asked Kent, BoDog's top bookmaker, for an update on the baseball season to date as well as the NBA and NHL playoffs.

In Kent's own words: "NBA has been very good for us. The biggest action has been on Sacramento each game, and they just haven't been as dominant over the Jazz as they were in the regular season. NHL has been good as well, and got off to a great start with the House cashing in on big New Jersey and Detroit money. However, the players have done very well in the last week with the Red Wings covering four straight. Baseball has been a roller-coaster ride, with the House getting beat bad the first week, but rebounding strong ever since. We were taking a huge amount of Yankees action and losing, as they went 7-1 to start the year, but since they lost four straight and six-of-seven a couple of weeks back, action has been far more balanced and we've been in the plus column since. Handle has been much higher than expected for baseball, and we look forward to a great Summer."

I'll be back in a couple of weeks with more analysis of the baseball season and the playoffs thus far.