Slots - FAQ

Do the casinos tighten and loosen the slots on a daily/hourly basis, to attract business when its slow and rake it in when its busy?

James from Cherry Hill, USA

The EPROM chips, which control the theoretical return percentages on slots, are generally changed very rarely. It would be bad business to loosen and tighten the slots according to the day of the week. For any given casino there is some optimal return to maximize profit. Wherever that is, a smart slot manager would find that point and then just leave the EPROMS set to that return.

Is there any ways to cheat the slot machines?

Michael V.

Sure. There are lots of ways. Putting in fake coins just to name a simple one. Be warned that in Nevada cheating in a casino carries the same kind of penalty as bank robbery, or so I hear. Let the record show that I disapprove of all forms of cheating.

I’m happy to see that you’re once again taking questions on your site. Being a math teacher, I especially love how me must pass the gauntlet of solving a basic, two-step algebra problem. My question pertains to the bonus rounds that are extremely prevalent in many of today’s slot machines. Are the bonus round winnings already pre-determined, even before I enter the new screen, or do my choices really affect my amount of winnings? On a game like Price is Right, for example, I seem to always win the lower of the two prizes in the bonus round. When it comes down to picking one of the two remaining tags, I always seem to pick the one giving me the less favorable outcome. Am I just continuously unlucky or does the machine already know that I will get the lower result before I even pick? Thanks so much. Keep up the great work!

Ara from Fresno

Thanks for the kind words. I always enjoy hearing from high school math teachers out there because I almost became one myself. Based on seeing par sheets and speaking to industry insiders I can confidently say that if the alternative choices are shown at the conclusion of a bonus round then the game is honest about them. In other words the prizes were randomly determined and what you see at the end is truly how they were hidden. However in games where the alternative choices are not shown the odds are likely similar to a prize wheel, with lower probabilities for the higher wins. I played Price is Right enough to see the Showcase Showdown twice. As you said, the values behind the price tags are revealed at the end. So I maintain that the game is indeed truthful and speculate that you have just been unlucky.

I like coming and checking on your website and reading your analysis of games and various probabilities. My question is one that I believe can only be answered by someone who is close to the slot machine industry. There is a slot machine that my girlfriend and I like to play. It is a regular three-reel slot machine with either quarter or dollar denominations. The fun part of the machine is if you get the "hamburger lady" in the 3rd reel and it starts a bonus game. The game involves the player pushing a button that starts a digital die moving and stopping on 1-6 and then the player moves along the hamburger and obtains credits as you go along ultimately trying to get to the top for the huge bonus of 5,000 credits. My question then is that is the bonus already decided for the player before the bonus starts or since after every die move the player has to push the button is the bonus amount completely random. There are various points in the bonus game that if you get a specific die roll the bonus will end but can the player avoid these early terminations or is the bonus amount predetermined even before the start of the game. I say that the bonus is predetermined but my girlfriend believes otherwise. Please help with this argument.

Pedram from Claremont

Your girlfriend is right. Nevada Gaming Control Board regulation 14.040.2(b) states...

"For gaming devices that are representative of live gambling games, the mathematical probability of a symbol or other element appearing in a game outcome must be equal to the mathematical probability of that symbol or element occurring in the live gambling game. For other gaming devices, the mathematical probability of a symbol appearing in a position in any game outcome must be constant."

In other words a representation of dice must have the same odds as real dice. Thus there would be no way to predestine an outcome because the player could roll anything during the course of the game.

In your March 27, 2006 column someone asked about who would win the money if someone put money into your machine and hit the spin button and won. You replied "According to my understanding of the law, the person who pressed the spin button wins the money. Whoever is sitting in front of the machine, and why, or even who put the money in, or even whose money it is, does not matter." Are you telling me someone can just run through a casino hitting other peoples spin buttons and any winnings are theirs to keep?

Nicole S. from Brooklyn

I asked three casino executives about this hypothetical situation. They all said that you can’t win a bet if you don’t make a bet. In the case where betting somebody else’s money is consensual then they will pay the person pressing the buttons. However in the case where it is not consensual they will not pay the person who pressed the button. A more difficult question is whether they will pay the person who did put money in the machine. That seems to be taken on a case by case basis. Considerations include whether the player was vigilant in guarding his machine, how much the player was playing for, and if he is a known good customer. Basically a player should follow the McDonald’s rule of "keep an eye on your fries." However even if the player was remiss in guarding his machine the casino may not want to anger a good customer. It also helps to be playing a high denomination game.

When the house awards me free play on a slot machine, ex. $100, how much does it actually cost them?

David from W. Palm Beach

It depends. If the slot play may be used in any machine in the casino, including video poker, then it can be worth 99 cents on the dollar or more, depending on the video poker offerings. For example, the MGM Mirage casinos award $1 in free slot play for every one point earned. It can be used in any machine in any casino connected to the MGM Mirage player card. Most MGM Mirage properties offer 9/6 Jacks or better, so the value of $1 in free slot play is worth 99.54 cents, with correct strategy.

However, sometimes free slot play must be done on particular promotional machines that don’t accept money. The value of this kind of free play is hard to estimate closely, but generally very little. For example, the Las Vegas World used to sell “$1000” vacation packages for $400. Of the alleged $1000 value $600 was in promotional slot machine play. In his book “Million Dollar Video Poker,” Bob Dancer writes that he did this deal numerous times over, and estimates the value of the free slot play to be about ten cents on the dollar.

What is an appropriate tip for the dealer (they keep their own tips) if a person hits a royal flush at Caribbean Stud if the JP is $230,000? Also, what would one tip for a straight flush if the gross pay was $23,600 but net $17,000 after 28% is withheld for federal taxes? Thank you. Love your website!

Judith H. from Chula Vista

Thanks. As I say about machine jackpots, 0.5% to 1% of the jackpot amount after taxes is good. Whether the dealers pool their tips or not should not make a difference.

Wizard, what do you think about the new "server based" slot machines currently being used at the Treasure Island in Las Vegas? Apparently this technology allows the casino to instantly change the machines from their back offices — including the games offered, denominations, and.....the payouts! I think this is going a bit far. I mean what’s to stop the house from targeting certain players (like the drunk high roller) and making it tougher for that player to win? We all know the casinos can pretty much keep an eye on any player they want to any time. Between the surveillance, and now this technology, it seems to give the house too much of an edge. Suppose a table player has a heated disagreement with a dealer or pit boss over a hand (which occasionally happens); now this same player goes to the slots and the house can extract revenge by making his machine pay out less??!! Of course they could "favor" certain players too...which could be just as dangerous. I’m all for allowing the games and denominations to be changed, but shouldn’t the regulators be involved when it comes to payout percentages???

Gary from Charolotte, NC

I asked a source of mine who works at one of the casinos that utilize this technology. Besides the Treasure Island, this technology is also used at casinos in California, Michigan, and Mississippi. Here is what he said,

"Nothing can be changed if there are credits on the game. The slot machine will always reject any changes sent when there are credits on the meter. In Nevada, the machine also has to be idle for four minutes prior to and following any changes. It’s also not completely transparent to anyone standing in front of the slot machine. A black window pops up that says ’Remote Configuration In Progress’ (or something like that).

We mainly use ours to change the available denominations on our games. Similar to how table games will raise minimum bets on when the casino is busier, we will remove lower denominations on Friday morning and return them on Monday morning."

So, rest assured, that the slot manager can not tighten up a game on you just because he doesn’t like you. As long as you have credit in the game, nothing can be changed.

Imagine a slot machine bonus with a field of icons. Some are prizes and some are "Party Poopers," for lack of another term. The player keeps all prizes he finds until he accumulates so many Party Poopers. Is there a formula for the number of prizes the player can expect to get?



p = Number of Party Poopers.
w = Number of wins.
e = Party Poopers needed to end bonus.

Imagine the w wins in a row, like a loaf of bread. Then place the p Party Poopers like raisins equaly along the bread, creating the same distance between consecutive raisins as well as from each end. For example, if the bread was 12" long, and you had 3 raisins, you would place the raisins at the 3", 6", and 9" points, creating 4 segments of 3" each.

The expected number of wins picked is the product of the length of each segment and the number of Party Poopers needed to end the bonus, or e × (w/(p+1)). Let's look at an example.

Suppose there is a field of 40 icons with 8 Party Poopers. It takes three Party Poopers to end the bonus. That would leave 32 wins. So, p = 8, w = 32, and e = 3. The expected number of successful picks is 3 × (32/(8+1)) = 32/3 = 10.67.

How do slot machine Community Bonuses work?


Community, or group, bonuses is a popular new concept in slot machines. While the bonus can be earned in different ways, depending on the game, the concept is that more than one player can play the same bonus round at the same time. Usually the outcome is shown on a large video screen visible to all players. One exception is the Wheel of Fortune community bonus, where an enormous wheel sits between the individual machines.

From what I can tell, the Wheel of Fortune community bonus is earned by an individual player achieving the initiating event on his own. It then starts a 10-second countdown, to give other players a chance to trigger a bonus. Usually this doesn't happen, so the player who earned the bonus plays by himself.

In contrast, on the American Idol slot machine, all active players play the community bonus. It is also triggered independently of where the reels stop, so no matter how many players are playing, or how fast they play, the odds of a bonus at any given time are always the same. The rest of this answer shall focus on how specifically the American Idol community bonus works.

It would be unfair if there were two players in a bank of community bonus machines, in which one was betting $1 a minute, and one was betting $10 a minute, if they both had the same expected value in the community bonus. To avoid such injustice, a multiplier is applied to the final bonus win, roughly according to the amount the individual player was betting at the time the bonus was initiated, factoring in both average bet and speed of play. How the game determines each player's multiplier is a bit complicated. Here is what I could figure out:

  • The game keeps track of the players' last 40 seconds of betting activity for each player, in the form of a queue.
  • Each 20 cents the player bets at one time buys him 10 seconds of 1x multipliers. So, a $1 bet would buy 10 seconds of 5x multipliers. This multiplier is added to the end of the player's queue.
  • If the player plays at a faster rate than one bet per ten seconds, causing there to not be enough space in the queue to add 10 seconds of multipliers, then it will cram any excess multipliers onto the last few seconds. How exactly it does this, I'm not sure.
  • As the player sits at the machine, the game will drop off from the stack the highest multipliers in the queue. Kind of like how in a queue for a Vegas nightclub it doesn't matter your position in line for girls, but how pretty you are; the most attractive girls are removed from the queue first.
  • As multipliers are dropped off the queue they are also the eligible multiplier should the community bonus be triggered at that moment.
  • At any given microsecond, except if a community bonus is already in progress, there is a fixed probability that the bonus will be triggered. So the time between bonuses would follow an exponential distribution. In other words, a bonus has a memoryless property and is never overdue, much like a royal flush in video poker.

Example: Let's say the player has 35 seconds of 1x multipliers in his queue. He then makes a $1 bet. Normally this would buy 10 seconds of a 5x multiplier. However, in this case there isn't enough room in his queue to add ten seconds. What the game would likely do is add four seconds of 1x multipliers, and one second of a 6x multiplier. I'm not saying it would do exactly this, but something along these lines, where the total time × average multiplier still equals 10.

Besides community bonuses, there are also "local bonuses" that are earned by each individual player and played only by that player. If a community bonus hits during a local bonus then that local bonus will be put on hold during the community bonus. To keep the local bonus player eligible for community bonus the game will give the player 60 seconds of multipliers. This is an exception to the usual 40-second queue. I am not sure how the multiplier during this time is determined. If the player finishes the local bonus in less than 60 seconds then the multipliers for the remaining time are somehow added to his queue.

One thing I have no idea about is what happens if a player sits down and starts playing during an ongoing community bonus, which the game will let him do. It would be unfair if the player were playing during this time without any chance to trigger another community bonus. I'm told that the machine somehow compensates the player in this situation, but I have no idea how.

This question was raised and discussed in the forum of my companion site Wizard of Vegas.

If you can shed any light on the unanswered questions in my answer, please feel free to write to me or post your comments in my forum.

What is your opinion of the player who was denied an $8.5 million slot machine jackpot at the Lucky Eagle Casino in Rochester, Wash. Seems she has a good case to me.

terapined from Tampa, FL

She was playing a 5¢ machine and the alleged win was $8,588,749.65. This number looked familiar to me as a power of 2. To be specific, 2^33 = 8,589,934,592. If this were a count of tenths of pennies, it would equal $8,589,934.592. The difference between that and the jackpot is $1,184.942.

What I think happened is the machine declared the win as an unsigned integer, meaning a number that could never go negative. However, through some programming error, it wanted to. When you try to put a negative number into an unsigned integer, the computer will wrap around the other end. In this case, I think something bizarre happened and through whatever programming error, the game thought the player had a loss of $1,184.942. When it tried to display this number as an unsigned integer, it wrapped around the maximum value and displayed the win of $8,588,749.65.

Every slot machine I've ever seen says somewhere "malfunction voids all pays and plays." If I were the judge, I would have to say that this was indeed a malfunction and side with the casino. This was, of course, what the casino argued. Nevertheless, their $80 compensation offer strikes me as very stingy.

More information at KATU.

For more discussion on this question, please see my forum at Wizard of Vegas.

Where do casinos put the loosest slots?


As a rule of thumb, the location makes no difference.