Craps is a dice game in which players place wagers on the outcome of the roll, or a series of rolls, of a pair of dice. Players may wager money against each other (street craps, also known as shooting dice or rolling dice) or a bank (casino craps, also known as table craps). Craps really isn’t complicated when you remember that the entire point is gambling on the sum on a pair of dice. One player rolls the dice, typically trying to get a 7 or 11. If they don’t get this number on the first roll, they establish a “point” number that they have to roll again before rolling a 7. Manipulating the roll of the dice (Dice Control or Dice Setting) is one of the most common methods for cheating in Craps. Holding the dice in a particular grip or throwing it in a certain manner lets players can gain a crucial edge over the house and other players at the table.
Alter then so that one die has a six on every side, and the other one has all ones and fives.
Thanks for the kind words. No, I don't think that wishful thinking helps in the casino, all other things being equal.
The question on the dice influence is a hotly debated topic. Personally, I'm very skeptical. As I review this reply in 2013 I still have yet to see convincing evidence anybody can influence enough to have an advantage.
I'm very skeptical of it. I go over some of the experiments on the topic in my craps appendix 3.
I don’t believe in it. So far I have yet to see a name I respect endorse the method, nor any evidence that it works. While I don’t entirely rule out the possibility I am extremely skeptical of it. I may live in Nevada but when it comes to things like dice setting I’m from Missouri, 'show me' it works.
With ordinary dice, the like those you get in a board game, this is true. However casino dice have inlaid spots. At the factory they drill holes for the spots then insert white colored spots into the holes, of the same density as the die itself. So the die is essentially a perfect cube. Even if they did use ordinary dice from a board game I doubt the bias would be nearly enough to overcome the house edge.
I think there is no such thing as a naturally bad shooter. With the possible exception of a few pros all dice throws can be considered truly random. There are seminars on how to overcome the house edge in craps by precession throwing but I make no claims for or against them. I have yet to see enough evidence either way.
I lost the $1800 to another gambling writer, not Stanford. I would have preferred more rolls but there was an obvious time contraint. Assuming one throw per minute it would take 34.7 days to throw the dice 50,000 times. I wasn’t the one who decided on 500 but it seemed like a reasonable compromise between a large sample size and time. You are right that 500 is too few to make a good case for or against influencing the dice, but 500 throws is better than zero.
For large numbers of throws we can use the Gaussian Curve approximation. The expected number of sevens in 655 throws is 655 × (1/6) = 109.1667. The variance is 655 × (1/6) × (5/6) = 90.9722. The standard deviation is sqr(90.9722) = 9.5379. Your 78 sevens is 109.1667 − 78 = 31.1667 less than expectation. This is (31.1667 - 0.5)/9.5379 = 3.22 standard deviations below expectation. The probability of falling 3.22 or more standard deviations south of expectations is 0.000641, or 1 in 1,560. I got this figure in Excel, using the formula, normsdist(-3.22).
This is about controlling the dice at Craps. You previously discussed the Stanford Wong Experiment, stating, 'The terms of the bet were whether precision shooters could roll fewer than 79.5 sevens in 500 rolls of the dice. The expected number in a random game would be 83.33. The probability of rolling 79 or fewer sevens in 500 random rolls is 32.66%.... The probability of rolling 74 or fewer sevens in 500 random rolls is 14.41%.'The question I have about this bet is that 14.41% still isn’t 'statistically significant' [ i.e. p < 0.05 ] , which is usually taken to mean greater than two Standard Deviations from the Mean -- or a probability of less than a *combined* 5% of the event happening randomly on EITHER end of the series.
How many Sevens would have to be rolled in 500 rolls before you could say that there is a less than 2.5% chance that the outcome was entirely random (i.e. that the outcome was statistically significant) ?
Many Thanks & BTW , yours is ABSOLUTELY the BEST web site on the subject of gambling odds & probabilities that I’ve found .... keep up the good work !!!
Thank you for the kind words. You should not state the probability that the throws were non-random is p. The way it should be phrased is the probability that a random game would produce such a result is p. Nobody expected 500 rolls to prove or disprove anything. It wasn’t I who set the line at 79.5 sevens, but I doubt it was chosen to be statistically significant; but rather, I suspect the it was a point at which both parties would agree to the bet.
The 2.5% level of significance is 1.96 standard deviations from expectations. This can be found with the formula =normsinv(0.025) in Excel. The standard deviation of 500 rolls is sqr(500*(1/6)*(5/6)) = 8.333. So 1.96 standard deviations is 1.96 * 8.333 = 16.333 rolls south of expectations. The expected number of sevens in 500 throws is 500*(1/6) = 83.333. So 1.96 standard deviations south of that is 83.333 − 16.333 = 67. Checking this using the binomial distribution, the exact probability of 67 or fewer sevens is 2.627%.
There is no definitive point at which confidence is earned. It is a matter of degree. First, I would ask what is being tested for, and what the shooter estimates will happen. With any test there are two possible errors. A skilled shooter might fail, because of bad luck, or a random shooter might pass because of good luck. Of the two, I would prefer to avoid a false positive. I think a reasonable test would set the probability of a false negative at about 5%, and a false positive at about 1%.
For example, suppose the claimant says he can average one total of seven every seven throws of the dice. A random shooter would throw one seven every six throws, on average. By trial and error I find that a test meeting both these criteria would be to throw the dice 3,600 times, and require 547 or fewer sevens to pass, or one seven per 6.58 rolls.
A one in seven shooter should average 514.3 sevens, with a standard deviation of 21.00. Using the Gaussian approximation, the probability of such a skilled shooter throwing 548 or more sevens (a false negative) is 5.7%. A random shooter should average 600 sevens, with a standard deviation of 22.36. The probability of a random shooter passing the test (a false positive) is 0.94%. The graph below shows the possibe results for skilled and random shooters. If the results are to the left of the green line, then I would consider the shooter to have passed the test, and I would bet on him.
The practical dilemma is if we assume two throws per minute, it would take 30 hours to conduct the test. Perhaps I could be more liberal about the significance level, to cut down the time requirement, but the results would not be as convincing. I do think the time has come for a bigger test than the 500-roll Wong experiment.
First of all, she rolled the dice a total of 154 times, with the 154th roll being a seven out (Source: NJ.com). However, that does not mean she never rolled a seven in the first 153 rolls. She could have rolled lots of them on come out rolls. As I show in my May 3, 2003 column, the probability of making it to the 154th roll is 1 in 5.6 billion. The odds of winning Mega Millions are 1 in combin(56,5)*46 = 175,711,536. So going 154 rolls or more is about 32 times as hard. Given enough time and tables, which I think exist, something like this was bound to happen sooner or later. So, I wouldn't suspect cheating. I roughly estimate the probability that this happens any given year to be about 1%.
Also see my solution, expressed in matrices, at mathproblems.info, problem 204.
I think some of the casinos in Las Vegas are using dice that are weighted on one side. As evidence, I submit the results of 244 throws I collected at a Strip casino. What are the odds results this skewed could come from fair dice?Dice Test Data | |
Dice Total | Observations |
2 | 6 |
3 | 12 |
4 | 14 |
5 | 18 |
6 | 23 |
7 | 50 |
8 | 36 |
9 | 37 |
10 | 27 |
11 | 14 |
12 | 7 |
Total | 244 |
7.7%.
The chi-squared test is perfectly suited to this kind of question. To use the test, take (a-e)2/e for each category, where a is the actual outcome, and e is the expected outcome. For example, the expected number of rolls totaling 2 in 244 throws is 244×(1/36) = 6.777778. If you don’t understand why the probability of rolling a 2 is 1/36, then please read my page on dice probability basics. For the chi-squared value for a total of 2, a=6 and e=6.777778, so (a-e)2/e = (6-6.777778)2/6.777778 = 0.089253802.
Dice Total | Observations | Expected | Chi-Squared |
2 | 6 | 6.777778 | 0.089253 |
3 | 12 | 13.555556 | 0.178506 |
4 | 14 | 20.333333 | 1.972678 |
5 | 18 | 27.111111 | 3.061931 |
6 | 23 | 33.888889 | 3.498725 |
7 | 50 | 40.666667 | 2.142077 |
8 | 36 | 33.888889 | 0.131512 |
9 | 37 | 27.111111 | 3.607013 |
10 | 27 | 20.333333 | 2.185792 |
11 | 14 | 13.555556 | 0.014572 |
12 | 7 | 6.777778 | 0.007286 |
Total | 244 | 244 | 16.889344 |
Then take the sum of the chi-squared column. In this example, the sum is 16.889344. That is called the chi-squared statistic. The number of 'degrees of freedom' is one less than the number of categories in the data, in this case 11-1=10. Finally, either look up a chi-squared statistic of 10.52 and 10 degrees of freedom in a statistics table, or use the formula =chidist(16.889344,10) in Excel. Either will give you a result of 7.7%. That means that the probability fair dice would produce results this skewed or more is 7.7%. The bottom line is while these results are more skewed than would be expected, they are not skewed enough to raise any eyebrows. If you continue this test, I would suggest collecting the individual outcome of each die, rather than the sum. It should also be noted that the chi-squared test is not appropriate if the expected number of outcomes of a category is low. A minimum expectation of 5 is a figure commonly bandied about.
Whether or not it is called a valid roll depends on where you are. New Jersey gaming regulation 19:47-1.9(a) states:
A roll of the dice shall be invalid whenever either or both of the dice go off the table or whenever one die comes to rest on top of the other. -- NJ 19:47-1.9(a)
Pennsylvania has the exact same regulation, Section 537.9(a):
A roll of the dice shall be invalid whenever either or both of the dice go off the table or whenever one die comes to rest on top of the other. -- PA 537.9(a)
I asked a Las Vegas dice dealer who said that here it would be called a valid roll, if it was otherwise a proper throw. Although he has never seen it happen, he said if it did the dealers would simply move the top die to see what number the lower die landed on. However, one can determine the outcome of the lower die without touching, or looking through, the top die. Here is how to do it. First, by looking at the four sides you can narrow down the possibilities on top to two. Here is how to tell according to the three possibilities.
This question was raised and discussed in the forum of my companion site Wizard of Vegas.
This question was asked at TwoPlusTwo.com, and was answered correctly by BruceZ. The following solution is the same method as that of BruceZ, who deserves proper credit. It is a difficult answer, so pay attention.
First, consider the expected number of rolls to obtain a total of two. The probability of a two is 1/36, so it would take 36 rolls on average to get the first 2.
Next, consider the expected number of rolls to get both a two and three. We already know it will take 36 rolls, on average, to get the two. If the three is obtained while waiting for the two, then no additional rolls will be needed for the 3. However, if not, the dice will have to be rolled more to get the three.
The probability of a three is 1/18, so it would take on average 18 additional rolls to get the three, if the two came first. Given that there is 1 way to roll the two, and 2 ways to roll the three, the chances of the two being rolled first are 1/(1+2) = 1/3.
So, there is a 1/3 chance we'll need the extra 18 rolls to get the three. Thus, the expected number of rolls to get both a two and three are 36+(1/3)×18 = 42.
Next, consider how many more rolls you will need for a four as well. By the time you roll the two and three, if you didn't get a four yet, then you will have to roll the dice 12 more times, on average, to get one. This is because the probability of a four is 1/12.
What is the probability of getting the four before achieving the two and three? First, let's review a common rule of probability for when A and B are not mutually exclusive:
pr(A or B) = pr(A) + pr(B) - pr(A and B)
You subtract pr(A and B) because that contingency is double counted in pr(A) + pr(B). So,
pr(4 before 2 or 3) = pr(4 before 2) + pr(4 before 3) - pr(4 before 2 and 3) = (3/4)+(3/5)-(3/6) = 0.85.
The probability of not getting the four along the way to the two and three is 1.0 - 0.85 = 0.15. So, there is a 15% chance of needing the extra 12 rolls. Thus, the expected number of rolls to get a two, three, and four is 42 + 0.15*12 = 43.8.
Next, consider how many more rolls you will need for a five as well. By the time you roll the two to four, if you didn't get a five yet, then you will have to roll the dice 9 more times, on average, to get one, because the probability of a five is 4/36 = 1/9.
What is the probability of getting the five before achieving the two, three, or four? The general rule is:
pr (A or B or C) = pr(A) + pr(B) + pr(C) - pr(A and B) - pr(A and C) - pr(B and C) + pr(A and B and C)
So, pr(5 before 2 or 3 or 4) = pr(5 before 2)+pr(5 before 3)+pr(5 before 4)-pr(5 before 2 and 3)-pr(5 before 2 and 4)-pr(5 before 3 and 4)+pr(5 before 2, 3, and 4) = (4/5)+(4/6)+(4/7)-(4/7)-(4/8)-(4/9)+(4/10) = 83/90. The probability of not getting the four along the way to the two to four is 1 - 83/90 = 7/90. So, there is a 7.78% chance of needing the extra 7.2 rolls. Thus, the expected number of rolls to get a two, three, four, and five is 43.8 + (7/90)*9 = 44.5.
Continue with the same logic, for totals of six to twelve. The number of calculations required for finding the probability of getting the next number before it is needed as the last number roughly doubles each time. By the time you get to the twelve, you will have to do 1,023 calculations.
Here is the general rule for pr(A or B or C or ... or Z)
pr(A or B or C or ... or Z) =
pr(A) + pr(B) + ... + pr(Z)
- pr (A and B) - pr(A and C) - ... - pr(Y and Z) Subtract the probability of every combination of two events
+ pr (A and B and C) + pr(A and B and D) + ... + pr(X and Y and Z) Add the probability of every combination of three events
- pr (A and B and C and D) - pr(A and B and C and E) - ... - pr(W and X and Y and Z) Subtract the probability of every combination of four events
Then keep repeating, remembering to add probability for odd number events and to subtract probabilities for an even number of events. This obviously gets tedious for large numbers of possible events, practically necessitating a spreadsheet or computer program.
The following table shows the the expected number for each step along the way. For example, 36 to get a two, 42 to get a two and three. The lower right cell shows the expected number of rolls to get all 11 totals is 61.217385.
Highest Number Needed | Probability | Expected Rolls if Needed | Probability not Needed | Probability Needed | Expected Total Rolls |
---|---|---|---|---|---|
2 | 0.027778 | 36.0 | 0.000000 | 1.000000 | 36.000000 |
3 | 0.055556 | 18.0 | 0.666667 | 0.333333 | 42.000000 |
4 | 0.083333 | 12.0 | 0.850000 | 0.150000 | 43.800000 |
5 | 0.111111 | 9.0 | 0.922222 | 0.077778 | 44.500000 |
6 | 0.138889 | 7.2 | 0.956044 | 0.043956 | 44.816484 |
7 | 0.166667 | 6.0 | 0.973646 | 0.026354 | 44.974607 |
8 | 0.138889 | 7.2 | 0.962994 | 0.037006 | 45.241049 |
9 | 0.111111 | 9.0 | 0.944827 | 0.055173 | 45.737607 |
10 | 0.083333 | 12.0 | 0.911570 | 0.088430 | 46.798765 |
11 | 0.055556 | 18.0 | 0.843824 | 0.156176 | 49.609939 |
12 | 0.027778 | 36.0 | 0.677571 | 0.322429 | 61.217385 |
This question was raised and discussed in the forum of my companion site Wizard of Vegas.
The Wizard says that website sounds like a lot of ranting and raving with no credible evidence whatsoever to justify the accusation. I'd be happy to expose any casino for using biased dice, if I had any evidence of it.
If anybody has legitimate evidence of biased dice, I'd be happy to examine it and publish my conclusions. Evidence I would like to see are either log files of rolls or, better yet, some actual alleged biased dice.
Furthermore, if the casinos really were using dice that produced more than the expected number of sevens, then why aren't these detectives privy to the conspiracy out there betting the don't pass and laying the odds?
My question is what is average bonus win?
Click the following button for the answer.
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Let x be the answer. As long as the player doesn't roll a seven he can always expect future wins to be x, in addition to all previous wins. In other words, there is a memory-less property to throwing dice in that no matter how many rolls you have already thrown you are no closer to a seven than you were when you started.Before considering the consolation prize, the value of x can be expressed as:
x = (1/36)*(1000 + x) + (2/36)*(600 + x) + (3/36)*(400 + x) + (4/36)*(300 + x) + (5/36)*(200 + x) + (5/36)*(200 + x) + (4/36)*(300 + x) + (3/36)*(400 + x) + (2/36)*(600 + x) + (1/36)*(1000 + x)Next, multiply both sides by 36:
36x = (1000 + x) + 2*(600 + x) + 3*(400 + x) + 4*(300 + x) + 5*(200 + x) + 5*(200 + x) + 4*(300 + x) + 3*(400 + x) + 2*(600 + x) + (1000 + x)When you visit Leelanau Sands Casino you don’t want to miss the craps table. Since it’s one of the most exciting tables games on our casino floor, you’ll often hear cheering around the craps table. Not sure how to play? Let us help!
Craps is a fairly simple game but can get complicated with the sheer number of bets you can make on the table and odds you need to keep track of.
Allow our experts to guide you through the basic rules of craps and teach you how to play…
What You Need to Know About Craps
Craps is one of the only games in the casino where a player is in charge of their own hand. Meaning, instead of you being dealt cards, you get to select and roll your own dice. The goal in craps is to predict how the dice will land.
The table is played in rounds with two phases in a round; the come out and point. Each player’s turn to roll the dice moves clock-wise around the table at the end of each round. There can be up to 20 players at a craps table and everyone will get a chance to throw the dice. If you don’t’ want to throw the dice, you can still play, but you bet on the shooter, or the person throwing the dice.
How Do You Play Craps at the Casino?
When it’s your turn to roll, you’ll be presented with five dice on the table, pick up two of them. You can only handle and throw these dice with one hand. Before you throw you must place a bet on the pass line or don’t pass line (more on this later).
First Phase in Craps: Come out
This is the first roll of the game and the black puck in the middle will say “Off.” A dice roll of 2, 3 or 12 (rolling these numbers is also known as craps) ends the roll and the players lose their bets on the Pass Line, but you get to roll again! A come out roll of 7 or 11 results in a win for bets on the pass line (this is the only time in craps where 7 is good!). The shooter will continue to make come out rolls until they roll a 4, 5, 6, 8, 9, 10. When they land on one of those numbers, it becomes the point. When this happens, the dealer moves the ON button to the point number on the table and this signifies the beginning of the second round.
To recap: Pass line bets on the come out roll: 7 or 11 wins; 2, 3, and 12 lose.
Second Phase in Craps: Point
In the second round, it’s the shooter’s goal to roll the point number they established in the first round.
If the shooter rolls a point number, it’s a win for bets on the pass line and you get to roll again. If the shooter rolls a seven before their point number they “seven out,” and have lost; bets on the pass line lose and the round ends.
To clarify, the first roll in a round is the come out roll and is the beginning of a new game. A come out roll can only happen after the previous shooter makes their point or rolls a seven. When this happens, the dice move to the left of the shooter (clock-wise).
Craps Table Layout
A craps table is divided into two sides, both a mirror image of each other, to allow bettors on each side of the table to play without reaching all over the table.
Each area on the table signifies a different bet.
How to Place Basic Craps Table Bets
There are dozens of bet variations you can place on a craps table, and we won’t cover all of them here.
1) Pass and Don’t Pass Bets
Two of the best and safest bets in craps are bets on the Pass and Don’t Pass lines. When you bet on the Pass line, you’re betting that the shooter will win. The opposite is true for the Don’t Pass line.
To place these bets, simply place your chips in these areas on the table before the come out roll. Once the point is established, you cannot remove your pass line bet. Be sure to ask the dealer if you have any questions before placing your bet!
2) Odds Bets
Once the point is established, you can place odds bets or “bet behind the line.” The odds bet is a great bet because the casino has no advantage. To make this bet, simply place your chips behind your bet in the pass or don’t pass line. These bets can be removed or changed at any time during the round.
3) Numbers Bets
During the points roll, you can place bets on certain numbers that are on the table. If they come up during the points roll, you win! Different numbers have different odds. When you want to place a bet on a number, place your chips in front of you and tell the dealer where you want your bet placed.
4) Field Bets
If you want to play the field, place your chips in this area on the table. If the dice lands on any of the numbers in the field (2, 3, 4, 9, 11, 12) you win! These are one-roll bets, meaning they removed after the dice is rolled.
Tips for Playing Craps
Play Craps in Leelanau County
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