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# Ask the Slot Expert: Do keno machines use RNGs?

31 January 2018

Question: In Las Vegas, do keno machines operate under an RNG as do poker and slot machines? Or are they independent of an RNG and determine the outcome based on the numbers you played that game?

The reason I ask is that all too often it seems I can play a five-number game for hours and the minute I change my numbers, those five come in? It could be coincidental, but it does seem to happen more often than it should.

Answer: How often has this happened to you? How many times have you changed numbers and had your old numbers come out and how many times have you changed numbers and not had your old numbers come out? And have you done the math to calculate how often it should happen?

If you don't keep records, the best you can say is that it "seems" to be happening. I've been caught in thinking that something seemed to be happening that wasn't really happening once I kept records.

Years ago IGT had a Double Diamond machine that would respin the third reel if the symbols on the first two reels were part of a winning combination. It seemed to me that the third reel almost always landed back on the same symbol when it respun. I mentioned this to the slot director at the casino. He said that as far as he knew, the program running the slot machine polls the RNG again to get a new stopping place for the third reel. The same symbol might come back, but different symbols should appear too.

When I actually kept track of the original symbol and the respin symbol, I quickly discovered that different symbols appeared quite frequently. I must have just had a number of spins that returned the same symbol when I developed my incorrect hypothesis. Every time I got the same symbol back reinforced my hypothesis and those instances weighed more in my mind than the times I got a different symbol. Without having written records, I was able to develop the impression that the same symbol came back much more frequently than a different symbol appeared.

My current misconception is that I get a natural high-paying hand more frequently when I play Deuces Wild than when I play Jacks or Better or Bonus Poker. The theory that someone could espouse for why this is happening is that the natural hand pays much less on the Deuces game so the machines give more natural hands when someone plays the Deuces paytable. Every time I get a natural hand on Deuces, I think, "What a waste. This would have paid so much more on Jacks or Better."

I haven't kept any records on this phenomenon yet, and I won't bother. I know that video poker machines deal cards without any regard for the pay table being played. (Well, the only time the pay table is taken into account is adding a joker to the deck when playing a Joker's Wild pay table. But then again, that doesn't affect card selection only deck composition.) The only time the pay table comes into play is when the end hand is evaluated and winning hands are paid. The cards are dealt using output from the RNG and the RNG is free of any outside influences.

Keno machines use an RNG to draw numbers. In fact, every electronic gaming device on the slot floor in Las Vegas, Atlantic City, Tunica and in all the other Class III casinos use an RNG to determine the results of a bet on the device.

Keep in mind, too, that no gaming jurisdiction would approve a machine that was programmed to draw numbers you had just stopped playing.

The probability of drawing the five numbers you just stopped playing is the same as the probability of drawing the numbers when you were playing them. The probability of drawing any set of five numbers is the same, regardless of whether you are playing them. I'm sure that machines have drawn your numbers right after you switched to different numbers. I'm also sure that you think it's happening more frequently that it's really happening. Not happening is not remarkable; it's what you expect to happen — after all, the machine just went through so many plays without drawing them. But when the machine does draw your numbers, the drawing really stands out in your mind and I bet you have some choice words for the machine too.

Speaking of the probability of drawing any set of numbers, I want to address something I heard on the Howard Stern Wrap-Up Show last week. The father of one of the writers on the show plays the lottery often and frequently chooses consecutive numbers. The producer said that that really struck him. When has the lottery ever drawn consecutive numbers, he asked? He implied that it is really unlikely to have consecutive numbers drawn.

Which is more likely in a lottery drawing: consecutive numbers or nonconsecutive numbers? Nonconsecutive numbers. There are many more sets of nonconsecutive numbers than consecutive numbers.

Now let's ask the question a little differently. Which is more likely in a lottery drawing: 1-2-3-4-5 or 1-2-8-13-24?

You might choose the second set, which is nonconsecutive, because we've already said that it's more likely that the numbers drawn in a lottery are nonconsecutive. But the first question just asked about consecutive versus nonconsecutive, not any specific set of numbers.

Once you specify the numbers, the probability of drawing each set is the same. The probability of drawing 1-2-3-4-5 is the same as that of drawing 1-2-8-13-24.

Even Marilyn Vos Savant got tripped up by thinking that a general case applies to a specific situation about seven years ago. I'll simplify the example a bit. A reader asked whether it was more likely to roll 11111 or 66234. Marilyn replied, "In theory, each result is equally likely." More than in theory, in fact. "Both specify the number that must appear each time the die is rolled."

So far, so good. But then she asks, if the die has already been tossed, which series is more likely to be the one thrown? "Because the roll has already occurred, the answer is (b). It's for more likely that the roll produced a mixed bunch of numbers than a series of 1s."

It's true that it's more likely that the series will be mixed than the same number. But once you specify the numbers, the probability of each series is the same. "Both specify the number that must appear each time the die is rolled."

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