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Ask the Slot Expert: How Do New Slot Machines Figure Out How Much to Pay?

7 November 2012

By John Robison

New slot machines are placed on the casino floor with a preset payback percentage, meaning in the long run the amount they pay depends on how much money is spent by customers.

The question, John, is, since they are new and no one has played them before, how do they calculate how much to pay the early players since little or no credits have accumulated yet?

Thank you for your clear, solid, and at times jolly replies in your column. God bless!

Washington Pete

Dear Pete,

Thanks for the kind words about my column.

Slot machines don't calculate how much to pay players. They choose the results of a spin at random without regard for what has happened in the past. It's possible for the very first spin by a patron on a machine to be the top jackpot.

The amount of money that has been played on a machine has no effect on the results of future spins. It's true, though, that in the long run the amount of money a machine has returned to its players will be very close to its long-term payback percentage. Because results are chosen at random, a 95% payback machine may have paid back anywhere from, say, 50% to 140% after 1000 spins. After 10,000 spins, the range might have narrowed to, say, 80% to 110%. I'm making up these numbers for a mythical slot machine, but slot manufacturers give casinos some statistics (confidence intervals and volatility index) to casinos to give them an idea of how close a machine's actual payback will be to its long-term payback after a certain number of spins.

Let's say slot machines did operate the way you described. Wouldn't a new machine have to have a long period of losing spins until it had collected enough money to start paying out?

Jackpots for all,
John


Hi John,

I recently got a very old dollar bill. I looked at it and I said, "I like those numbers." I'm not one to play keno, but I went to a five-cent machine and played the numbers on my old dollar bill. I hit all seven numbers and won $350 (I had only one coin in).

Would I have hit if I'd played a max bet?

Congratulations on your jackpot.

Chances are, you would not have received the same numbers had you bet the maximum. You would have had to have hit the Draw button at the exact same instant to receive the same numbers. It probably would have taken you a little more (or less) time to play the max bet, so the RNG would have been in a different point in its cycle and you would have received different numbers for that game.

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