Keno machines and randomness

22 September 2013

By John Grochowski

QUESTION: Does a keno machine contain a random number generator chip, or does the chip contain specific sets of numbers which have been predetermined and programmed into the chip and will be displayed, albeit even randomly, each time a customer presses the “lay” button?

It does not appear to me that if the chip in the machine could be truly a random number generator. How could a casino adhere to the percentage paid back per state requirements?

ANSWER: Video keno machines use a random number generator, and it generates a separate number for each number drawn. It does not generate specific sets of numbers.

This results in a predictable payback percentage because of the odds of the game. To use the very simplest example, let's say you're marking just one number, and if it is one of the 20 numbers drawn, you get a three-coin payback. We know there are 20 chances in 80 for one number to be drawn. On the average, per 80 draws, you will win 20 times and lose 60 times.

If you're betting one coin per draw, then in 80 draws you risk 80 coins. On each of the 20 on which your number is drawn, you get three coins back. So at the end of an average 80 draws, you have 60 coins. With 60 coins returned to you per 80 draws, the machine is paying 75 percent.

There are winning streaks, there are losing streaks, and in the short term the machine can pay a lot more or a lot less than 75 percent. But in the long run, over hundreds of thousands of plays, the odds of the game lead it inexorably toward that figure.

That's something casinos count on at every game, electronic or live at the tables. In the short term, there can be big winners at blackjack, slots, Big Six -- anything. Casinos count on winners to keep players coming back. If there were no winners, there would be no business. But the casinos also count on the odds of the game pulling long-term results toward an expected percentage.

QUESTION: Here's a question I can't get a straight answer on.

Assuming a three-reel stepper slot, is there a random number generated for each reel to determine their stopping position -- that is, three separate numbers for the three reels? Or is a single number generated that describes the stopping position of all three reels?

It would appear to me that a separate number would be generated for each reel. Each reel would have 128 or 256 or whatever total virtual positions to pick from.

If the final positions of all the reels were determined by a single number, then it would be possible to program the slot to never hit certain combinations while still coming up with the desired payout percentage.

ANSWER: There is a separate random number for each reel. I was told this a number of years ago by a former IGT engineer, then confirmed it when a source shared the PAR sheets on some popular games. The sheets show each number that is mapped to each symbol or space on the reel, and all three reels are mapped separately.

By the way, it is illegal in every American gaming jurisdiction to advertise a combination that it's impossible to hit.