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Do Patterns on Slots Disprove Randomness?

27 January 2005

I realize you are a very busy man answering all these nitpicking questions, but I am still awaiting an answer to a question I submitted several months back.

It was regarding play on a 10x, 50-cent machine, that showed the 10x symbol coming up above the center line three times in succession and then the next two times in succession below the center line. The next six spins repeated the above placement as the first and again the next six spins repeated the exact pattern as the two above. This was shown on the first reel of a three-reel machine. The same pattern three times!!!

In my interpretation of this, it definitely does not show randomness of an RNG. I have read all your very informative articles for the past four years and I already know what your answer will be. It will sure take some convincing to tell me that this is randomness as per the RNG.

Sorry to push you on this as you have more questions than time, I would imagine.

Phil

Dear Phil,

Today's your lucky day. Instead of answering the other questions that have been waiting for months, I bumped your current message right to the top of the queue because it's a good one.

I have a question first, though. If you already know what my answer is going to be, why are you so anxious to get it? :-)

Seriously, random does not mean that there is never a pattern. If a coin toss never resulted in streaks of heads or tails or a series of heads and tails alternating, then we would question the fairness of the coin. Streaks and patterns are perfectly good results for a random event.

In fact, one of the tests for the randomness of an RNG is to look for streaks and patterns and to see whether they occur with the frequency one would expect.

Here's another thing to keep in mind. You said you saw the 10X symbol landing above the payline. What you really saw was the blank below the 10X symbol landing on the payline. And I bet you that that blank appears on the virtual reel many times. The slot programmers tend to make the blanks near jackpot symbols fairly likely to land on the payline to generate some near-the-payline near misses.

Also, there might be more than one place on the physical reel where a 10X symbol is over a blank. Thus, given the many different virtual stops that could result in showing a 10X symbol over an on-the-payline blank, you may have actually seen a different virtual stop chosen on each spin.

I did a quick search of some definitions of "random" and some of them do say something like without order or pattern. Those definitions aren't very good. We really need a more mathematically precise definition. A reasonably good one is: a random event is an event that is affected by no input or state and whose result cannot be anticipated. In other words, nothing in the environment influences the result; the current result has no influence on the next result; and there is no way to determine what the next result will be. A mathematical definition of randomness doesn't say anything like "without order or apparent reason."

The testing laboratories test the RNG in a slot machine very thoroughly. Just because a pattern appears occasionally on a slot machine, that doesn't raise any doubts about the randomness of the RNG.

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. Because of the volume of mail I receive, I regret that I can't send a reply to every question. Also be advised that it may take two or more months for your question to appear in my column.

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