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# Gaming Guru

### Odds Once Again

27 July 2013

I recently received a letter from a reader named John regarding the odds involved in an odd/even or red/black roulette wager.

FROM JOHN: Since there are 18 winning spaces and 20 losing spaces on the wheel the true odds will be 20 to 18 or 2 to 1.8.

If the “actual odds” are 16 to 10 or 1.6 to 1. My question is how do you come up with the actual odds? It doesn't sit right with me.

MY ANSWER TO JOHN: John the simple answer is I don’t know how one would arrive at 1.6 to 1; I certainly did not promote this figure. Moreover it is worth pointing out that in past articles I have tried to emphasize that odds per se have nothing to do with chances or probability.

Odds are simply payoff ratios.

In the Roulette bets under consideration the odds are 1:1 or so called even odds. You either win or lose one unit. The only odds that take into account probabilities are the aforementioned true odds. “True odds” is the payoff structure that one would use if the game were fair, that is, no house edge. The calculation is simple:

20 x 1.8 – 18 x 2 = 0

A game’s operator can set the odds anyway he wishes independent of the probabilities; the true odds are unique and result in a game with zero expectation. See you in a couple of months.

[Want more about roulette? Read Frank Scoblete’s “Casino Conquest: Beat the Casinos at Their Own Games!” www.frankscoblete.com]

Don Catlin can be reached at 711cat@comcast.net
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Donald Catlin
Don Catlin is a retired professor of mathematics and statistics from the University of Massachusetts. His original research area was in Stochastic Estimation applied to submarine navigation problems but has spent the last several years doing gaming analysis for gaming developers and writing about gaming. He is the author of The Lottery Book, The Truth Behind the Numbers published by Bonus books.

#### Books by Donald Catlin:

Lottery Book: The Truth Behind the Numbers
Donald Catlin
Don Catlin is a retired professor of mathematics and statistics from the University of Massachusetts. His original research area was in Stochastic Estimation applied to submarine navigation problems but has spent the last several years doing gaming analysis for gaming developers and writing about gaming. He is the author of The Lottery Book, The Truth Behind the Numbers published by Bonus books.

#### Books by Donald Catlin:

Lottery Book: The Truth Behind the Numbers