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# More on Randomness

7 February 2005

Dear John,

In your last article, you wrote: "Today, it's unusual at all to hit a jackpot over that amount, especially on high-limit machines."

Didn't you mean: "today, its NOT unusual"?

Just clarifying.

Thanks for the articles.

Jerry

Dear Jerry,

You are absolutely right. I've corrected the article.

Thanks for catching my mistake.

Best of luck in and out of the casinos,
John

Mr. Robison,

You recently responded to a question regarding the apparent nonrandom appearance of symbols on a video slot machine and answered the question, but I'm not sure it was the correct answer.

I'm not an expert on slot machines, statistics, or human psychology but I suspect that given the quantity of computing capacity in the typical modern slot machine that there is a bunch of psychology going on (there is far far too much circuitry to be just a simple random number generator, video card, and such).

If you assume that a slot reel has 100 positions, the probability of a specific symbol appearing on the pay line is 1 in 100 or 1 in 33 1/3 if you include it appearing on, above or below the pay line. If a reel has one winning symbol, say "10X" then it would show in the "window" only once in every 33 1/3 opportunities (given a sufficiently large number of chances to demonstrate the statistics).

One way of encouraging continued play would be to tease the player by showing the "10X" symbol more frequently above or below the payline than an average of once every 33 1/3 opportunities. I believe that in most cases the probability of winning on any specific single play is random but that the selection of symbols appearing on the screen is not necessarily random.

Also, I sometimes think that today's video slots contain an empathy chip that controls payout, it senses that the more you want to win the less likely it is to hit--just kidding.

George

Dear George,

I loved the old Odd Couple TV series. One of my favorite episodes is when Felix is on trial and he riffs on the dangers of making assumptions. "When you assume," he said, "you make an ASS out of U and ME."

Your conclusions about the frequency with which you'd see the 10X symbol are correct given your assumptions, but no reel-spinning slot machine works that way.

The probability of landing the symbol on the payline is determined by the number of times the symbol appears on the virtual reel. The probability that the symbol will land one stop above or below the payline is determined by the number of times the adjacent symbols appear on the virtual reel.

Slot designers generate these "near-the-payline" near misses by loading up the virtual reel with occurrences of the symbols near the 10X symbol. The virtual stop is still chosen completely at random, but the symbols don't appear on or near the payline with the same frequency because they do not appear the same number of times on the virtual reel.

Sometimes it does seem as if the machine knows what is happening. You can be running low on funds and the machine turns colder than an Antarctic winter and drains you dry in no time at all. But then other times, the machine will give you a nice hit when you're almost broke and keep you in the game for a while longer. It's all random!

Best of luck in and out of the casinos,
John

Here's a reply from Phil, who started this discussion about randomness with pattern he saw while playing a slot machine.

I can understand your reasoning on random patterns on coin flipping. As I understand all writeups on RNGs, the selection is being generated hundreds or thousands of time per second and the selection is made from one chance in many thousands to line up a winning combination. This is a far cry from the 50/50 chance of coin flipping.

I see too many thousands of variations of numbers that cannot be grouped together to form a pattern. This would be a phenomenal occurrence that defies all odds, in my estimation. Even one grouping of the three above the center line and two below would blow my mind. Can you imagine the odds of this happening three consecutive times?

Maybe I don't see the forest for the trees but some day when you have some spare time, would you try and enlighten this old man?

Please continue your writings of that column as they are the most informative of all gaming articles.

Phil

Dear Phil,

You ask, "Can you imagine the odds of this happening three consecutive times?" You're assuming the pattern you saw is very unlikely, but I think the pattern you saw is far more likely to occur than you think. You're thinking that only one out of the thousands (or tens of thousands) of combinations of virtual stops on the machine leads to the pattern you saw.

Without having the layout of the virtual reels, there's no way to know exactly how many combinations result in the pattern you saw. Nevertheless, I do know that the blanks immediately above and below the jackpot symbol tend to appear pretty frequently on the virtual reel and thus have fairly high probabilities of landing on the payline. In addition, there's usually two jackpot symbols on each physical reel, each surrounded by blanks that appear many times on the virtual reel. That makes many more than one combination of virtual stops that leads to your pattern.

Thanks for the kind words about my articles. I really appreciate it.

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 several 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