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Best of John Robison

Gaming Guru

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IGRA Classes of Gaming, What is the RNG?, Megabucks, Double Diamond

25 March 2004

You say that each spin is random on a slot machine, and that there are, what, 8,000 combinations on a typical slot machine. Whatever the number, it must be calculated at more than the times I've played, if that is the case. Why do I recognize so many of the losing combinations that come up? And why do the same combinations seem to come up so often? Can't this be interpreted as a way to "read" the slots, as far as predicting that the next spin will be another "no win"?

Is there any way to determine how many winning symbols there are on a specific column? For example, three sets of cherries on the first reel, two sets on the second, one set on the third? Is it better to play a slot machine that has only five types of payouts, with all the symbols being made up of a variety of one type (e.g., different colored sevens)?

Yes, the result of each spin is determined at random. There are far more than 8,000 combinations on today's typical slot machines. The number is more like 32,000 or more.

This is the number of combinations based on the number of virtual stops on the reels. On a machine with 22 symbols and blanks per reel, there are only 10,648 (22x22x22) possible physical combinations of symbols. Each physical combination will appear more than once on the virtual reels.

That may be one reason why you recognize so many of the losing combinations. Another is that the virtual reels are usually set up such that a losing combination like bar-bar-blank will land more frequently than one like blank-bar-bar.

There's no way to "read" the slots. The result of each spin is determined at random. And since most machines have hit frequencies below 50%, you can predict that the next spin will be a "no win" and be right more than half the time.

There's also no way to determine how many times a symbol appears on a virutal reel. Besides, even if you knew that the cherry appeared five times, that wouldn't help you because you also need to know how many stops there are on the virtual reel.

You can however figure out the probability of landing any particular symbol on any reel. All you need to do is play or watch someone play the machine and note the combinations that land on the payline for a few thousand spins. Count up the number of times each symbol appeared on each reel and divide by the number of spins to get an estimate of landing a symbol on a reel.

As for your last question, it isn't any better or worse to play a machine that has only a few winning combinations. These machines have both high and low-payback programs available, so they're not necessarily better or worse than any other type of machine.

Best of luck in and out of the casinos,
John


In IGT's Double Diamond and Triple Diamond slots, with the big variance of payout in the multliplied wins, does that mean that the Triple Diamond slot is programmed with the RNG to have less of a pay cycle than that of the lower Double Diamond slot? I imagine this holds true in the 5-Times Pay versus the 10 Times Pay machines also.

Thanks! I enjoy reading your informative comments!

Phil

Dear Phil,

It's true that the higher the multiplying symbol on a machine, the lower the hit frequency tends to be, but that has nothing to do with the RNG. Just like in the prior answer in this column, it's all in the virtual reels. The layout of the symbols on the virtual reels determine the hit frequency and payback of a machine.

RNGs generate numbers--nothing more, nothing less. There's no such thing as a loose or a tight RNG. RNGs are also not programmed to have "pay" and "take" cycles.

And neither are slot machines programmed to have pay cycles. These cycles do seem to occur, but they're just the result of the random selection of outcomes, just as a coin toss has streaks of heads and tails. The coin doesn't decide to start landing on heads, and the program in the machine doesn't decide it's time to start paying for a while.

Best of luck in and out of the casinos,
John


Dear John,

I truly enjoy reading your column on the slots.

In reference to your reply to Dale on January 29, you stated that Indian casinos may have Class II gaming devices.

What's the difference in Class II and any other gaming devices? How many different classes are there?

Are the Indian casinos nationwide like this or just in Iowa?

Thanks, Jim

Dear Jim,

The three different classes of gaming and gaming devices are defined in the Indian Gaming Regulatory Act (IGRA).

Class I gaming is defined as "social games solely for prizes of minimal value or tradition forms of Indian gaming engaged in by individuals are a part of, or in connection with, tribal ceremonies or celebrations."

Class II gaming includes bingo, pull-tabs and scratch-offs, lotto, and other games similar to bingo.

Class III is everything else, including banking card games and Las Vegas-style slot machines.

So, what's the difference between a Class II and a Class III device. In a Class III slot machine, the RNG in the machine is used to determine the result of a spin. No other device is used. Class II devices are not allowed to determine their own results, just as a bingo card alone cannot determine the result of a bingo drawing.

In much the same way that a bingo drawing determines the winners and losers in a game of bingo, the RNG in another device must determine the winners and losers on the Class II devices. These devices essentially turn a bingo drawing into a slot machine. Each slot machine has its own bingo card to use in determining spin results. The central computer draws some number of numbered balls and sends the results of the drawing down to the slot machines, which determine which symbols to show on the payline based on the pattern covered on their bingo cards.

Frank Scoblete and I have consulted with manufacturers about the design of both Class II and Class III devices. The implementation of a Class II device is rather complicated and arcane compared with the simplicity and elegance of a Class III device. Nevertheless, IGT and Bally are both designing Class II versions of their most popular Class III machines.

Indian casinos need state compacts in order to offer Class III gaming. They don't need compacts to offer Class II gaming, so that's why we have these "bingo machines in slot machine's clothing."

Best of luck in and out of the casinos,
John


What is the RNG?

Regards,
Betty

Dear Betty,

RNG stands for Random Number Generator. The RNG is a special function in the computer program running the slot machine that generates a series of numbers. You can make your own simple RNG by tossing a pair of dice repeatedly and noting the sum of the dice on each throw. In the slot machine, the RNG is a set of mathematical functions.

The slot machine uses the numbers from the RNG to determine which symbols to land on the payline. For example, the number from the RNG might be 1,283,345, which might correspond to Megabucks-Megabucks-Blank. Better luck next time!

Best of luck in and out of the casinos,
John


Question about Megabucks progressive slots in Nevada: I read that the winning jackpot amount is set at some random value greater than the minimum, and that when the progressive pot reaches this value, the next spin wins. Any idea whether there is any truth to this?

There's no truth whatsoever to the statement.

Each Megabucks machine contains its own RNG and determines the results of its spins. The progressive is hit when someone happens to hit the Spin button just when the RNG on that machine has generated a value that corresponds to three Megabucks symbols.

It is true, however, that each machine reports back to the progressive link controller, which is in Reno for Megabucks. When a jackpot is hit, the signal goes out to the appropriate Jackpot Team to go to the casino to verify the win. Just as important, the progressive amount is reset to the minimum and the new value is sent out to all the machines to display.

I've heard tell that the simultaneous groans from all the Nevada Megabucks players when they see the progressive reset is so loud that IGT can hear it all the way up in Reno, but I think that's just an old wive's tale.

Best of luck in and out of the casinos,
John


Send your slot and video poker questions to John Robison, Slot Expert, at slotexpert@comcast.net.

John Robison

John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots
John Robison
John Robison is an expert on slot machines and how to play them. John is a slot and video poker columnist and has written for many of gaming’s leading publications. He holds a master's degree in computer science from the prestigious Stevens Institute of Technology.

You may hear John give his slot and video poker tips live on The Good Times Show, hosted by Rudi Schiffer and Mike Schiffer, which is broadcast from Memphis on KXIQ 1180AM Friday afternoon from from 2PM to 5PM Central Time. John is on the show from 4:30 to 5. You can listen to archives of the show on the web anytime.

Books by John Robison:

The Slot Expert's Guide to Playing Slots