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# Is there a way to determine a machine's long-term payback?

11 January 2010

Is there a way to test a machine's payout percentage?

For pooled machines linked to a jackpot, is the payout percentage still per machine or can it be spread out across the total machines in the casino?

If you say higher denominations pay out better, then wouldn't you agree they have a separate RNG or seed, since it is the only variables that can change the payout? Therefore, pulling 30 no-wins on .10 then changing to 1.00 isn't going to help.

Are there any books written by ex-IGT or Bally's manufacturing people with this inside knowledge that could be useful?

Rodney

Dear Rodney,

There is a way to determine a machine's long-term payback percentage. If you total the amount of money you win on each spin and divide that number by the total amount you bet on all spins, the result will be the machine's long-term payback. Unfortunately, machines are so volatile that you'd have to play 10,000,000 or so spins to get a good estimate.

Fortunately, there's another method. If you keep track of how often each symbol lands on the payline on each reel, you can estimate the probabilities of landing those symbols. With those probabilities you can estimate the probabilities of landing each winning combination. Once you know how likely it is to land each winning combination, you can calculate the machine's long-term payback. This method takes only a few thousand spins.

As for your second question, I don't know of any jurisdiction that allows a casino to meet the statutory minimum payback by aggregating machines. Each machine's long-term payback must by equal to or greater than the statutory minimum.

I wouldn't say that higher denominations pay out better. I would say that they do have higher long-term paybacks. I think that saying that they "pay out better" implies that they hit more frequently, and that's not necessarily true.

I also wouldn't agree that higher denominations have a separate RNG. The RNG does not change the payback percentage. Changing the reel layout or changing the pay table changes the payback. The RNG itself is random, and therefore neutral.

There are no current books on slots written by former employees of IGT, Bally's or any other manufacturer. The ones that may still be on the market are out of date; some of the information in them is no longer true. Slots have changed quite a bit in the last 10 years.

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 reply to every question.

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