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Best of John Robison

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Slot Machine Hit Frequency and RNG

19 April 2001

Dear John,

  1. Is there any way to determine the hit frequency of a particular machine without playing the machine?
  2. Are the newer video - electronic machines programmed any differently or is the functioning of the RNG the same as in an older one-line mechanical slot?

Thanks in advance,
SJ

Dear SJ:

  1. No. Unless you have the par sheet, which is the document on file at the casino and at the regulators that describes how a machine is programmed, there's no way to know the hit frequency of a slot machine without playing it. A thousand spins is enough to give you a fairly accurate estimate.
  2. I'm going to take the opportunity to dispel some myths about the RNG with my answer to this question.

The RNG in a video slot can be identical to the RNG in a reel-spinning slot and even to one in a video poker machine. The only purpose of the RNG is to generate a stream of random numbers. The programs in those different machines, however, may do different things with the stream of numbers.

The program in a reel-spinning slot, for example, will take one or more numbers from that stream and that number or numbers tell the program which stops will land on the payline. Actually, there's an intermediate step on most machines. The random number chooses a virtual stop from the virtual reel, which exists only in the machine's programming. The virtual reel has many more stops on it than the physical reel. The virtual reel is used to make some physical stops less likely to land on the payline than others. The virtual reel is what makes the odds of landing a Megabucks symbol on the payline 1 out of about 360 instead of 1 out of 22.

A common misconception is that some RNGs are looser than others and a casino has to change the RNG to loosen or tighten a machine. Not true. To alter the payback on a machine, they change the way the virtual reel is mapped to the physical reel. The RNG stays the same.

In a video slot, there is no need for this intermediate step (which is called Telnaes mapping) because there is no physical reel. The reel on a video slot can be as large as its programmers want it to be. Just as with the program in a reel-spinning slot, the program in a video slot uses the output from the RNG to choose which stop will land on the payline. And the RNG algorithm itself can be identical to one in an older slot.

Best of luck in and out of the casinos!
John


Send your slot and video poker questions to John Robison, Slot Expert, at slotexpert@home.com.


For more information about slots and video poker, we recommend:

The Slot Expert's Guide to Playing Slots by John Robison
Break the One-Armed Bandits! by Frank Scoblete
Victory at Video Poker and Video Craps, Keno and Blackjack! by Frank Scoblete
Slot Conquest Audio Cassette Tape (60 minutes) with Frank Scoblete
Winning Strategies at Slots & Video Poker! Video tape hosted by Academy Award Winner James Coburn, Written by Frank Scoblete
The Slot Machine Answer Book by John Grochowski
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