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Best of John Robison

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Why is a slot like tossing a coin?

23 October 2006

Hello, John,

I enjoy reading your newsletters to see what other slot players say and your responses.

Recently you made the following comment regarding random hits and I've seen you use it many times before:

"Well, what would you see if you flipped 20 fair coins? Sometimes the number of heads and tails is roughly even. Sometimes there are more of one side than the other, sometimes a lot more."

The slot machines have virtual reels in them with up to 640 (it may be some other similarly large number, but you can correct me on the actual number) stops on each reel. In your example using the coin, there are only two possible "stops".

Please explain how the coin example relates to a virtual reel with regard to multiple machines all hitting at the same time, as in the letter you were referring to.

It seems to me that the odds of three virtual reels all stopping on matching symbols is about the same as winning the lotto, whereas the chances of getting 20 two-sided coins to hit on the same side is quite good.

Please explain how three virtual reels are the same as three coins being tossed in the air.

Sincerely,
Mark

Dear Mark,

Tossing a coin is like getting a hit on a slot machine because they are both binary decisions. There are only two possible outcomes. For the coin, the outcome is either heads or tails. For the slot, the outcome is either hit or no hit.

They are different, however, in their probabilities. For the coin, the probability of heads or tails is 0.5. For the slot, the probability of a hit is probably much less than 0.5 for a reel-spinning slot and possibly much more for a video slot.

The writer of the original letter claimed that if slots were truly random, we wouldn't see hot rooms and cold rooms. Instead, we'd see the odd hit here and there.

The coins in my coin flip analogy are truly random and we see all sorts of outcomes — mostly heads, mostly tails and roughly even. The presence of streaks does not indicate something is not random.

Seeing banks, rooms, or even entire casinos hot or cold does not indicate the machines are not random. It's hard not to believe that the bank of machines that were red hot last night and ice cold this morning have not been changed in some way, but it's all just a consequence of randomness.

Best of luck in and out of the casinos,
John


We have all heard that casinos have some machines that hit better than others, they call these machines loose machines and they are few and far between in the casinos that I have played at.

I'm starting to understand the RNG and that every jackpot that I have hit wasn't because I believed that the machine was due to hit something, but that I hit the spin button at that precise moment in time that the RNG was at the jackpot. In other words... Lucky.

So what constitutes a loose machine? Does it let you play longer without devouring your bankroll? Does it hit more jackpots more often? Is this machine a 99% payback machine vs. the 91% machine? And the most important question... What is different about the RNG that makes these slots looser than others?

I'm assuming that it's a computer programming process, but after reading a few of your comments on RNGs and how they transfer to the reels, then maybe that's where the difference is. Maybe it's the reels or even both, the RNG and the reels. Are all RNGs generating the same amount of numbers? Ok, let's say there are 2 million sets of numbers the RNG can generate from on machine A (tight machine). Can machine B (loose machine) only have 1.5 million sets of numbers to generate from?

Part 2: There's a machine at my favorite casino that I believe is a loose machine, several secondary jackpots, and if anything, it lets me play without devouring my bankroll. This particular machine is also a multi-denomination machine and I've read in your columns, that it only has one RNG for this machine, even though it has four denominations to choose from.

So, I'm thinking, loose machine, why not play a higher denomination? Will the machine still play as loose at a higher denomination? I had always thought that each of the multi-denomination machines were like four different machines in one machine, with four different programs or four different RNGs so I was apprehensive to play the higher denominations. Now that I know differently, maybe I should try to play this machine at $2, $5, or even $10. What say you?

Really enjoy your columns and thanks for sharing your knowledge to all of us slot junkies.

Tim

Dear Tim,

Thanks for the kind words about my column.

There is no standard definition of a loose machine, although I think everyone would call a machine with a long-term payback of 99% and above loose.

The looseness of a machine is tied to its long-term payback, not its hit frequency. Long-term payback and hit frequency are independent. A loose machine does not have to hit more frequently than a tight machine.

But it's difficult to convince players that a 99% payback machine with a low hit frequency is a loose machine when the hits are few and far between. So, many players call high hit frequency machines loose, even though these machines might have low long-term paybacks. Video slots hit often and appear loose, for example, but their long-term paybacks are not necessarily high.

As far as I'm concerned, a loose machine is the Holy Grail of slot machines. It can mean whatever you want it to mean and you can go on your own search for it if you wish.

The RNG has nothing to do with looseness and long-term payback. Slot programmers change the long-term payback of a machine by changing the distribution of symbols on the virtual reels, not by changing the RNG.

As for the multi-denomination machine, it may or may not have the same virtual reel layouts for the different denominations. As a general rule, video poker pay tables increase in long-term payback as you go up in denomination on a multi-denomination machine, so I would expect the paybacks of the slot games to increase with denomination too. Unlike video poker, there's no way to tell the long-term payback of a slot machine, so we don't know for sure on any particular machine.

Even if the machine you've found is truly a loose machine, keep in mind that it still pays back less than 100% in the long run. You should only move up in denomination if you have the bankroll to support moving up.

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