Identifying Biased Roulette Wheels

How to clock a wheel

french_rouletteThe basic method to determine whether a particular roulette wheel is biased or not is known as ”clocking”. It refers to collecting and recording the winning numbers as they occur. The simplest way of doing this is with the help of a piece of paper and a pen. Someone may ask whether casino personnel are likely to ask him/her to stop doing this. Well, players who have done this first hand say that if one is marking the winning numbers on a paper while seated at the roulette table, casino staff may not pay attention so long as he/she also continues placing his/her bets. In case one becomes quite successful, a member of casino personnel may grow curious about the playing system being used. In case the winning streak continues even further, the staff member may ask the player to cease marking the winning numbers on a paper, but yet it is not 100% sure. The reason for it is the uncertainty whether the player will be forced to cash in his/her chips and leave after the request from the staff member. In case one does not take part in the playing session, he/she may feel free to mark the numbers on paper as long as he/she wishes. Although there is no law that prohibits wheel clocking, one should avoid ”standing in the spotlight”. It may be better, if he/she maintains a low profile.

It is a practice in a number of casinos each roulette wheel to be rotated by a small amount (1/8 turn) on a weekly basis. It is done mainly in order to redistribute the wear on the ball track and to avoid groove development on the side where the dealer releases the roulette ball. Another trick used by casinos in order to make the work of wheel clockers more difficult is moving the roulette wheel from one table to another. Thus, if one is to clock a particular wheel, he/she needs to identify it first as well as its position on the roulette table. He/she needs to look for any individualistic characteristics and mark them on a piece of paper. One needs to look for any kind of imperfections – scratches in the finish, wear patterns, discolorations and so on. Having marked them, when he/she returns to the same table at some time later, he/she needs to ensure that the same wheel characteristics are present.

The winning numbers should be marked in the order, which they occurred. One needs to be sure that no number is skipped. Professional clockers usually collect at least 400 winning numbers, on which they base their preliminary decision about the wheel’s possibilities. In case the wheel seems to have some bias, clockers will mark another 1000 numbers as confirmation. However, in order to come across a potentially-biased wheel, a clocker may need to collect preliminary data for a number of wheels.

Roulette wheel and a winning number

How to clock a multitude of wheels

In some casinos one could be able to clock more than one wheel simultaneously. In case he/she encounters two, three or more wheels in one and the same pit, or grouped closely together, there may be no obstacle to clock all of them at the same time. In that case one needs only to make sure he/she did not mix the data from the different wheels.

Modern casinos and some of the older ones have installed electronic display boards (reader boards), which reflect the latest 16 or 21 winning numbers (depending on the reader model). Every time a new number is announced as a winner, it is put on the top of the board, while the oldest number is scrolled off the bottom of the board. These boards are a perfect opportunity for wheel clockers, as this way they are able to clock more wheels at the same time.

A clocker can usually rely on reader boards. However, occasionally one of the boards may not function properly. The issue may appear as the board showing a spurious repeat number. In case a clocker comes across a board with repeat numbers, he/she will need to observe the roulette wheel for a while and confirm that the numbers are indeed repeating. It is best to observe the wheel one is clocking for some 15-20 spins, before he/she can focus his/her attention on the reader board entirely.

Roulette wheel and winning number

Wheel Identification

After a clocker has collected enough data for a specific wheel, he/she needs to evaluate it in order to decide whether the wheel shows any biases. At first, he/she needs to determine which numbers in the set of data have occurred most frequently. On a double-zero wheel the probability of success for any particular number is 1/38, or once every 38 wheel spins. The number, which tends to win the most, would be occurring more often than the average. Someone may ask what frequency of occurrence a clocker would consider outside the normal range for a random wheel. The answer is obviously statistical in its nature and is linked to significance tests and confidence levels, which we shall avoid.

Experts in the field propose the following rule: In case a particular number wins 10 or more times in 200 spins and its both adjacent numbers also surpass the average of 5.3 wins in 200 spins (valid only for a double-zero wheel), one should pay a closer attention to that roulette wheel. In case in 200 spins the number 17 comes up 11 times, this occurrence will not be significant by itself. However, if in addition the adjacent numbers came up at least 7 times each, a clocker will certainly need to examine that wheel. As the probability of success is 1/38, the particular winning number is anticipated to occur 2.63% of the time. If a number wins 11 times in 200 spins, then it is expected to occur 5.50% of the time (11 / 100 = 0.055), or a bit more than twice the expected rate. This alone does not deserve attention. Actually, in case that number came up twice that often, the wheel would still be considered as random. If, on the other hand, both adjacent numbers also won more often than anticipated, this would suggest a normal distribution curve (a bell-shaped curve).

European Roulette Wheel

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