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# Ask the Slot Expert: Calculating the long-term payback of an online slot

8 May 2013

I was trying to deconstruct some slot machines to be able to calculate probabilities and return. I recorded a video [of some Boss Media-based slots] and started taking note of each symbol in the order they showed on the reels, and noticed that the sequence seemed to be random because I couldn't find a pattern to determine the whole reel strip. I've read that some games can have up to 300 virtual stops, but I have already reached that quantity and couldn't find a repetition.

Can it be that symbols show in a random way while the reel is spinning, or the slots hold hundreds of virtual stops for each reel?

What is the best approach to determine how many symbols of each type are on the reels?

The animation you see on a video slot is not the actual spinning of the reels. Most video slots have a sequence of animations they go through to display the reels starting to spin, spinning and then slowing down. It's only when the reels stop that what you see really exists in the programming of the machine. What you see is like a cheap cartoon that reuses footage over and over. I assume that online slots work the same way.

So, you can't try to reconstruct the video reels by slowing down the spinning animations. You should be able to reconstruct the reels by noting the symbols you can see after the reels have stopped and piecing those snippets together.

To calculate a machine's long-term payback, though, you don't really need to know the layout of the virtual reels. All you need to know is each symbol's probability of landing on the payline on each reel. If you keep track of how many times each symbol lands on the payline on each reel, you can calculate estimates of the probabilities -- and your estimates get better with each play. I think you'll find estimating probabilities to be the easiest way to calculate a machine's long-term payback.

Jackpots for all,
John

The other day I was playing a slot machine in A.C. I think the bet was 40 cents. The slot machine awarded me 50 free spins. My total winnings from the 50 free spins was less than \$9.

My question is, does the slot machine go into a different program mode (with lower paybacks) when the free spins are awarded?

Thanks,
Dennis

Dear Dennis,

The machine might use the same reels for the free spins or it might use different reels. Machines frequently say that special bonus reels are used when the reels are not the same.

In your case, it doesn't sound like you went into a "free spin bonus round." It sounds like you just won some free spins. In this case, the reels are usually the same as those used for a paid spin.

Cold streaks can happen during free spins, in addition to during paid spins. I think that's what happened to you. I recently won some free spins (not 50, about 10) on a slot and didn't win a single thing on them. At least you won toll money on yours.

Jackpots for all,
John

Hi John:

I just have a simple question: For the Goldfish and Goldfish 2 Slots, do you happen to know the music used by WMS? It seems so familiar from the '70s, yet I can't quite put my finger on it. I have been trying to find out for over a month by doing Web searches... and then... your name popped into my head as the best source of information!

-Harry

Dear Harry,

Thanks for the kind words about my columns.

I'm pretty sure that the music on those machines was commissioned for use on them. Licensing existing music is usually very expensive. Manufacturers usually promote the fact that a machine features music that people have heard and I couldn't find any mentions that these machines feature songs from the past.

If anyone knows that these machines are using existing music, please let me know.

Jackpots for all,
John

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