A martingale is any of a class of betting strategies that originated from and were popular in 18th century France. The simplest of these strategies was designed for a game in which the gambler wins the stake if a coin comes up heads and loses it if the coin comes up tails. The strategy had the gambler double the bet after every loss, so that the first win would recover all previous losses plus win a profit equal to the original stake. The martingale strategy has been applied to roulette as well, as the probability of hitting either red or black is close to 50%.

Since a gambler with infinite wealth will, almost surely, eventually flip heads, the martingale betting strategy was seen as a sure thing by those who advocated it. None of the gamblers possessed infinite wealth, and the exponential growth of the bets would eventually bankrupt 'unlucky' gamblers who chose to use the martingale. The gambler usually wins a small net reward, thus appearing to have a sound strategy. However, the gambler's expected value does indeed remain zero (or less than zero) because the small probability that the gambler will suffer a catastrophic loss exactly balances with the expected gain. (In a casino, the expected value is negative, due to the house's edge.) The likelihood of catastrophic loss may not even be very small. The bet size rises exponentially. This, combined with the fact that strings of consecutive losses actually occur more often than common intuition suggests, can bankrupt a gambler quickly.

Intuitive analysis[edit]

Split Bet – This is a bet on two numbers that are next to each other on the roulette table (not the roulette wheel). Street Bet – Bets on three numbers that are a Street on the roulette table. For example, 1,2,3 is a Street, 4,5,6 is a Street and so on. Corner Bet – A bet on four numbers that make a square on the roulette. Oct 29, 2019  A bet on “black” in Roulette has a probability of 18/38 of winning. If you win, you double your money. You can bet anywhere from $1 to $100 on each spin.a. Suppose you have $10, and are going to play until you go broke or have $20. The martingale strategy has been applied to roulette as well, as the probability of hitting either red or black is close to 50%. Since a gambler with infinite wealth will, almost surely, eventually flip heads, the martingale betting strategy was seen as a sure thing by those who advocated it.

The fundamental reason why all martingale-type betting systems fail is that no amount of information about the results of past bets can be used to predict the results of a future bet with accuracy better than chance. In mathematical terminology, this corresponds to the assumption that the win-loss outcomes of each bet are independent and identically distributed random variables, an assumption which is valid in many realistic situations. It follows from this assumption that the expected value of a series of bets is equal to the sum, over all bets that could potentially occur in the series, of the expected value of a potential bet times the probability that the player will make that bet. In most casino games, the expected value of any individual bet is negative, so the sum of lots of negative numbers is also always going to be negative.

The martingale strategy fails even with unbounded stopping time, as long as there is a limit on earnings or on the bets (which is also true in practice).^[1] It is only with unbounded wealth, bets and time that it could be argued that the martingale becomes a winning strategy.

Mathematical analysis[edit]

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The impossibility of winning over the long run, given a limit of the size of bets or a limit in the size of one's bankroll or line of credit, is proven by the optional stopping theorem.^[1]

Mathematical analysis of a single round[edit]

Let one round be defined as a sequence of consecutive losses followed by either a win, or bankruptcy of the gambler. After a win, the gambler 'resets' and is considered to have started a new round. A continuous sequence of martingale bets can thus be partitioned into a sequence of independent rounds. Following is an analysis of the expected value of one round.

Let q be the probability of losing (e.g. for American double-zero roulette, it is 20/38 for a bet on black or red). Let B be the amount of the initial bet. Let n be the finite number of bets the gambler can afford to lose.

The probability that the gambler will lose all n bets is qⁿ. When all bets lose, the total loss is

${\displaystyle \sum _{i=1}^{n}B\cdot 2^{i-1}=B(2^n-1)}$

The probability the gambler does not lose all n bets is 1 − qⁿ. In all other cases, the gambler wins the initial bet (B.) Thus, the expected profit per round is

${\displaystyle (1-q^n)\cdot B-q^n\cdot B(2^n-1)=B(1-(2q{)}^n)}$

Whenever q > 1/2, the expression 1 − (2q)ⁿ < 0 for all n > 0. Thus, for all games where a gambler is more likely to lose than to win any given bet, that gambler is expected to lose money, on average, each round. Increasing the size of wager for each round per the martingale system only serves to increase the average loss.

Suppose a gambler has a 63 unit gambling bankroll. The gambler might bet 1 unit on the first spin. On each loss, the bet is doubled. Thus, taking k as the number of preceding consecutive losses, the player will always bet 2^k units.

With a win on any given spin, the gambler will net 1 unit over the total amount wagered to that point. Once this win is achieved, the gambler restarts the system with a 1 unit bet.

With losses on all of the first six spins, the gambler loses a total of 63 units. This exhausts the bankroll and the martingale cannot be continued.

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In this example, the probability of losing the entire bankroll and being unable to continue the martingale is equal to the probability of 6 consecutive losses: (10/19)⁶ = 2.1256%. The probability of winning is equal to 1 minus the probability of losing 6 times: 1 − (10/19)⁶ = 97.8744%.

The expected amount won is (1 × 0.978744) = 0.978744.
The expected amount lost is (63 × 0.021256)= 1.339118.
Thus, the total expected value for each application of the betting system is (0.978744 − 1.339118) = −0.360374 .

In a unique circumstance, this strategy can make sense. Suppose the gambler possesses exactly 63 units but desperately needs a total of 64. Assuming q > 1/2 (it is a real casino) and he may only place bets at even odds, his best strategy is bold play: at each spin, he should bet the smallest amount such that if he wins he reaches his target immediately, and if he doesn't have enough for this, he should simply bet everything. Eventually he either goes bust or reaches his target. This strategy gives him a probability of 97.8744% of achieving the goal of winning one unit vs. a 2.1256% chance of losing all 63 units, and that is the best probability possible in this circumstance.^[2] However, bold play is not always the optimal strategy for having the biggest possible chance to increase an initial capital to some desired higher amount. If the gambler can bet arbitrarily small amounts at arbitrarily long odds (but still with the same expected loss of 1/19 of the stake at each bet), and can only place one bet at each spin, then there are strategies with above 98% chance of attaining his goal, and these use very timid play unless the gambler is close to losing all his capital, in which case he does switch to extremely bold play.^[3]

Alternative mathematical analysis[edit]

The previous analysis calculates expected value, but we can ask another question: what is the chance that one can play a casino game using the martingale strategy, and avoid the losing streak long enough to double one's bankroll.

As before, this depends on the likelihood of losing 6 roulette spins in a row assuming we are betting red/black or even/odd. Many gamblers believe that the chances of losing 6 in a row are remote, and that with a patient adherence to the strategy they will slowly increase their bankroll.

In reality, the odds of a streak of 6 losses in a row are much higher than many people intuitively believe. Psychological studies have shown that since people know that the odds of losing 6 times in a row out of 6 plays are low, they incorrectly assume that in a longer string of plays the odds are also very low. When people are asked to invent data representing 200 coin tosses, they often do not add streaks of more than 5 because they believe that these streaks are very unlikely.^[4] This intuitive belief is sometimes referred to as the representativeness heuristic.

Anti-martingale[edit]

This is also known as the reverse martingale. In a classic martingale betting style, gamblers increase bets after each loss in hopes that an eventual win will recover all previous losses. The anti-martingale approach instead increases bets after wins, while reducing them after a loss. The perception is that the gambler will benefit from a winning streak or a 'hot hand', while reducing losses while 'cold' or otherwise having a losing streak. As the single bets are independent from each other (and from the gambler's expectations), the concept of winning 'streaks' is merely an example of gambler's fallacy, and the anti-martingale strategy fails to make any money. If on the other hand, real-life stock returns are serially correlated (for instance due to economic cycles and delayed reaction to news of larger market participants), 'streaks' of wins or losses do happen more often and are longer than those under a purely random process, the anti-martingale strategy could theoretically apply and can be used in trading systems (as trend-following or 'doubling up'). (But see also dollar cost averaging.)

See also[edit]

Best Bet On Roulette Wheel

References[edit]

1. ^ ^abMichael Mitzenmacher; Eli Upfal (2005), Probability and computing: randomized algorithms and probabilistic analysis, Cambridge University Press, p. 298, ISBN978-0-521-83540-4, archived from the original on October 13, 2015
2. ^Lester E. Dubins; Leonard J. Savage (1965), How to gamble if you must: inequalities for stochastic processes, McGraw Hill
3. ^Larry Shepp (2006), Bold play and the optimal policy for Vardi's casino, pp 150–156 in: Random Walk, Sequential Analysis and Related Topics, World Scientific
4. ^Martin, Frank A. (February 2009). 'What were the Odds of Having Such a Terrible Streak at the Casino?'(PDF). WizardOfOdds.com. Retrieved 31 March 2012.

Remember to stay realistic about the long odds on this popular game of chance. Approach roulette with the sober realization that, with a house advantage of 5.26 percent on the American wheel, roulette is among the worst bets in a casino. Despite the odds, you can still use some simple strategies to stretch your roulette bankroll and enjoy the thrill of the spin. This article contains a few tips that can help you improve your chances of winning.

Roulette is a drain on your wallet simply because the game doesn’t pay what the bets are worth. With 38 numbers (1 to 36, plus 0 and 00), the true odds of hitting a single number on a straight-up bet are 37 to 1, but the house pays only 35 to 1 if you win! Ditto the payouts on the combination bets. This discrepancy is where the house gets its huge edge in roulette.

Starting with the basics

Strategy is critical if you want to increase your odds of winning. The first time you play roulette, the players sprinkling the layout with chips may look as if they’re heaping pepperoni slices on a pizza. You can make many different bets as long as you stay within the table’s maximum limits. Consequently, few players make just one bet at a time.

Of course, the more bets you make, the more complicated and challenging it is to follow all the action. Here are two possible plans of attack to simplify matters:

• Stick to the table minimum and play only the outside bets. For example, bet on either red or black for each spin. This type of outside bet pays 1 to 1 and covers 18 of the 38 possible combinations.

• Place two bets of equal amounts on two outside bets: one bet on an even-money play and the other on a column or dozen that pays 2 to 1. For example, place one bet on black and one bet on Column Three, which has eight red numbers. That way, you have 26 numbers to hit, 4 of which you cover twice. You can also make a bet on red and pair it with a bet on Column Two, which has eight black numbers. Again, you cover 26 numbers, and 4 of them have two ways to win. Pairing a bet on either red or black with Column One (or on one of the three dozens) covers 24 numbers, and 6 numbers have two ways of winning. Spreading bets like this won’t make you rich, but it does keep things interesting at the table.

Playing a European wheel

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If you happen to find a single-zero European wheel, you greatly improve your odds: The house edge is half that of roulette with the American wheel — only 2.63 percent. You may see a European wheel at one of the posh Vegas casinos, such as Bellagio, Mirage, or Caesars Palace. If you can’t find one on the floor, it’s probably tucked away in the high-limit area along with the baccarat tables, so you may need to ask. You can also find the single-zero wheel at some other upscale casinos around the country.

Because casinos set aside the European wheel for high rollers, you’re likely to find a higher table minimum, say $25. But because the house edge is half that of a double-zero wheel, the European wheel is the better roulette game to play for bigger bettors.

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Your chances of winning get even better if the casino offers an advantageous rule called en prison. Sometimes available on the European wheel, the en prison rule lowers the house edge even further to a reasonable 1.35 percent. The rule applies to even-money bets. For example, say you have a $10 bet riding on black. If the ball lands on zero, your even-money bet doesn’t win or lose but remains locked up for one more spin. If the ball lands on black on the next spin, the house returns your original bet of $10, but you don’t win anything. If the ball lands on red, you lose. And if the ball repeats the zero number again, your bet stays imprisoned for another round.