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# What is the relationship between hit frequency and the RNG?

7 March 2009

What is the relationship between a slot machine programmed hit frequency and the RNG?

Can a slot truly be called random if there is a predetermined number of winning combinations, big or small, per 1,000 plays or whatever frequency is programmed into the machine's computer?

You often state in your column that the final position of the reels on a reel slot, as example, are not predetermined and are based on the RNG assignment at the time the handle is pulled or the button is pushed. A predetermined number of winning positions suggests that there are exceptions to computer random choices.

Does this also explain how the house wins a percentage over the life of the machine? This seems to hit at the heart of slot play and would be useful information. Can you please clarify?

I am a fan of your articles and enjoy play in Wendover and Las Vegas, Nevada.

Thank you!

Thanks for the kind words about my articles.

There is no relationship between a slot machine's hit frequency and the RNG. The RNG merely provides a stream of random numbers, which are used to select stops on the virtual reels. The layout of the symbols on the virtual reels determines the machine's hit frequency.

You can think of the RNG as a lumberyard providing the raw material to builders, cabinetmakers and carpenters. They all start with the same raw material, but do very different things with it.

The same RNG function can be used to determine results on a Megabucks machine, on a 99% payback machine, and on an 82% payback slot at McCarran. The RNG is just raw material; the virtual reels determine long-term payback and hit frequency.

Moving on to your second question, there is no predetermined number of winning combinations per a certain number of plays. A 20% hit frequency doesn't say that you will absolutely get 20 hits for every 100 spin. It says that on the average you will get 20 hits per 100 spins. You may get 17 hits on the next 100 spins; you may get 25. You won't necessarily get exactly 20. But if you looked at the number of hits over 1,000 or 10,000 or 100,000 spins, you would find the hit frequency to be very close to 20%.

The house wins in the long run because, like at roulette and craps, it pays less than true odds when the player wins. A simple example is a machine with 10 stops on each of three virtual reels. The machine has a total of 1,000 (10x10x10) combinations. If we add up the amounts that can be won on the winning combinations and find the total to be 950 coins, the machine would have a 95% long-term payback. If it paid back true odds, the total would be 1,000 coins.

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