Ask the Slot Expert: Long-term payback, hit frequency and near misses on slot machines

Question: I read your recent column about the frequency of losing combinations with great interest. The letter mentioned a Double Diamond machine. I once was chatting with a slot manager at a casino in A/C years ago who mentioned, if I got this right, that they could order a Double Diamond machine in about 20 different “configurations”. Certainly, the payout percentage would be one of the variables in the configuration, say 96% or whatever, and how it paid off was another configuration variable. That I took to mean that giving a cherry every other spin might result in the same overall payout, 96% in my example, if the machine only maybe had one huge jackpot a day. I said that playing a machine like that, with apparently endless losing combinations, would be demoralizing beyond belief for a player.

He then said something interesting, that while a loss was a loss, how the machine displayed that loss was "advertising" and shuffled off. I thought, could they buy a machine that was configured to present more tantalizing losing combinations?

I noted a couple of interesting sentences in your response: “The designers did not go through every number from the RNG and assign it a stop on the virtual reel.” And: “The designers associated symbols with stops on the virtual reels.”

Could they "pepper" the machine with more RNGs that result in "close call" loses? They would not have to go through every RNG, but maybe put in 10% that resulted in a "close, but no cigar" loss?

Players are always trying to figure out an angle and maybe this is no more than a similar, likely fruitless, attempt to decode the “mystery” of a slot machine, but I will leave you with a personal experience.

I was playing at a casino in Wheeling, WV, a while back and centered in on a row of maybe five or six $5 Double Diamond machines. I took a seat at the end of the row and it seems like just after a couple of spins, two double diamonds showed in the first two reels and, my heart pounding, I stared at the blank that rolled into the last slot. My unreasoning brain thought, So close! Let me try again! And again. And again. After about $300 and one or two small wins, here came the two double diamonds in the first two slots followed by another blank.

About the same time, maybe just a couple of spins later, the lady on the last machine in the row to my left out an expletive of disgust and disappointment. I looked over the see what the matter was and saw she had the two double diamonds and the blank as I have had. She said, putting her fists on the machine, that was like the third time it happened. I told her, "Me too!" My initial thought, reasonable or not, was that they programmed the machine to display losing draws that way more frequently. It could have been all reasonable and random, but I cashed out and moved on.

Answer: Most slot machines have multiple long-term paybacks available for them. When slot directors order a machine, they choose the long-term payback they want for the machine. I've seen paybacks for a machine range from the low 80s to the high 90s.

Players don't really experience long-term payback. The reason why is right in the name of the statistic: long-term. It can take hundreds of thousands of spins for a player's actual payback on a machine to zero in on the machine's long-term payback. Many players never play that many spins on a machine in their lifetime, let alone in an individual session.

Players, on the other hand, do experience another slot statistic, hit frequency, because most machines zero in on their hit frequencies after a hundred or so spins. Some players like machines that hit small amounts frequently. Others prefer machines that pay larger amounts less frequently. Slot designers decide the playing experience they want for a particular slot title. They then try to keep that experience, which is achieved through the hit frequency, the same across all the long-term paybacks available for a machine.

Players want a Blazing 7s machine, for instance, to hit the combinations of 7s frequently and they're willing to give up on combinations of bars to get more ways to hit the 7s. The slot designers won't create a version that hits lots and lots of bars and rarely hits 7s. Likewise, if a machine is known as a high hit frequency machine, the designers won't create a low hit frequency version.

It's like McDonald's making a Big Mac taste the same whether you buy it in Kansas City, Kennebunkport or Kalamazoo.

It's surprisingly easy to increase long-term payback while keeping hit frequency the same. All the designers have to do on a Double Diamond machine, for instance, is change some of the single bars on the virtual reels to double or triple bars. The hit frequency stays the same because there aren't any more winning combinations, but the long-term payback goes up because some of those winning combinations pay more.

A losing spin that's a near miss is much more exciting than one that isn't. Landing Double Diamond - Double Diamond - blank on the payline will get your heart racing, while landing a blank on the first reel will just get you anxious for the end of the spin.

All machines are designed to display these tantalizing losing combinations. But they're all a result of how the symbols are placed on the virtual reels.

There are two types of tantalizing losing combinations: near-the-payline and on-the-payline.

Slot designers make high-paying symbols land above or below the payline frequently by placing the blanks above or below the high-paying symbols many times on the virtual reels. Even though it's the blank landing on the payline, players see the jackpot symbol just missing the payline. Slot regulators acknowledge that these near-the-payline near misses are misleading -- they don't mean the machine is trying to pay -- so they limit the number of times blanks above or below high-paying symbols can land on the payline relative to the high-paying symbol itself. Generally, the blanks can't appear more than six or seven times as frequently as the high-paying symbol.

The losing combination you described, Double Diamond - Double Diamond - blank, is an on-the-payline near miss. Slot designers create these types of near misses by placing very few of the high-paying symbols on the third virtual reel.

Altering the number of times a symbol appears on the reel is the only way slot designers can affect the frequency of the losing combinations today. Thirty or so years ago, the slot designers at Universal used a different method. They thought that if the spin was going to be a loser anyway, why not make it tantalizing? Their machines used a secondary decision to select an exciting losing combination after the RNG was used to determine that the spin was going to be a loser.

Slot regulators determined that this secondary decision was misleading because the frequency with which a symbol landed on the payline had no relation to the number of times it was on the virtual reel and gave players the misperception that the jackpot was more likely to hit than it actually was. They outlawed the secondary decision. Slot regulations usually state that the result determined by the RNG must be displayed without any alteration or secondary decisions whatsoever.

My answer to your question about whether a casino could buy a machine that was configured to present more tantalizing losing combinations is yes and no. Yes because near misses are a natural consequence whenever you can see the stops above and below the payline. And no because the machines can't be configured to make, say, 25% or 50% of the losing combinations tantalizing. The only way to affect the frequency of interesting losing combinations is to alter the layout of the symbols on the reels.

As for "peppering the RNG" with near misses, let's look at what happens when you start a spin on a traditional three-reel machine. After you start the spin, the program running the machine gets a number from the RNG, 123,546, for example. The program then divides that number by the number of stops on the virtual reel, say, 32 and takes the remainder. Dividing 123,456 by 32 gives a remainder of 0. The stops are numbered from 1 to 32, so we need to add 1 to the remainder. The number 123,456 from the RNG corresponds to stop 1 on the first virtual reel.

Now it's time for the program to determine where to stop the second reel. It gets another number from the RNG, does the division and gets the remainder, and adds 1 to the remainder to choose a stop on the second virtual reel.

The program repeats the process for the third reel and any other reels the machine has.

The RNG is pure. All it does is generate numbers. The RNG has no idea whether a number it generates corresponds to a blank or a Double Diamond. The mathematicians who designed the RNG function can't make it generate more close calls. The slot designer, however, can control the frequency of those close calls by how frequently the symbols appear on the virtual reels.

The goal of an RNG is to make each virtual stop on a virtual reel to be equally likely to be chosen. The RNG can't be altered to make virtual stop 7 more likely to be selected than virtual stop 13.

You can think of the RNG as the electricity entering your home. The same flow of electrons can be used to light a light, power your TV, charge your cell phone or run your computer.

Electricity is electricity. It's up to whatever you plug into the outlet to do something useful with it.

Similarly, the stream of numbers generated by the RNG is just a stream of numbers. It's up to the program running the slot machine to do something useful with them.

Send your slot and video poker questions to John Robison, Slot Expert™, at slotexpert@slotexpert.com. Because of the volume of mail I receive, I regret that I can't reply to every question.

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