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How can slots be random if…

By John Grochowski


It’s hardly news to informed slot players that the games are designed to yield random results and that there’s nothing you can do to make winners come up more often nor identify when the big hits might be coming. The games don’t have pre-programmed patterns of hot streaks nor cold streaks, or do they have to go into any makeup time after a big hit.

You’ve heard all that before, but do you believe it?

Nothing in the universe is perfectly random, but slots are as random as humans can program a computer to be, and certainly as random as roulette, craps or any other casino game. Still, players spot patterns in short-term results, and wonder if randomness is really all it’s cracked up to be.

Often, those who see patterns write to ask how their experiences can be squared with random results. Why are there more jackpots on busy nights? How can a programmed payback percentage be random? Let’s take a few of those questions from the email bag try to clear the random fog:

Slot machine results remain random no matter how many people are playing, and the casino employee that the player consulted knows that. More money will be paid out when more people are playing just because more wagers are being made. The payback percentages remain the same, the chances of any individual winning or losing remain the same, and the casino will both take in and pay out more money.

Let’s make up a hypothetical casino filled with machines set so the odds will yield a top jackpot once per 25,000 plays. And let’s compare a slow night with 100 players each spinning the reels 1,000 times vs. a crowded night with 1,000 players at 1,000 spins each. Our small crowd gets in a total of 100,000 spins, while the busy night brings one million spins. In an average session, the group of 1,000 players will see 40 jackpots, while the group of 100 players will see only four.

On every slot machine in a licensed casino, the results are determined by a random number generator. The casino can’t control when the payouts come. Still, if you have 10 players sitting at a bank of dollar machines, it’s more likely that at least one of them will hit a big pay than if only one customer is playing, just because more spins of the reels mean more chances for that big win to come up.

That’s all the casino employee was saying, in many fewer words. It’s not that the casino controls payouts so there are more in big crowds. It’s that the natural odds of the game lead toward more payouts when the reels spin more times.

That mix—programmed, yet random—is something that has confused many a player in the decades since slots went electronic. Slot manufacturers must program payback percentages to comply with the law in states that set minimum and maximum returns. And the machines still have to be able to meet state randomness standards.

The confusion seems to be over exactly what it is that the programmer is programming. It’s not a matter of telling the game that it must pay a designated percentage. It’s a matter of setting the possibilities and the odds of the game so that random results eventually will lead to the desired return.

In that way, slots are like table games. Take roulette. On an American double-zero wheel, the game is “programmed” with 38 possible results—numbers one through 36 plus 0 and 00. The numbers come up randomly, and when you win on a single number, you’re paid at 35- 1 odds, a bit less than the true odds of 37-1. That gives the house an edge of 5.26 percent, or to turn it around, gives the game a programmed payback percentage of 94.74 percent.

There is nothing to keep your number from coming up two or three times in a row, and nothing that says it has to come up within several dozen spins or more. But given enough trials, the random results and the odds of the game will lead to something very close to roulette’s “programmed percentage.”

Slots work more or less the same way, except that there are thousands of possibilities instead of 38. For regular play on the reels, randomly occurring numbers are programmed, each corresponding to a reel symbol. To make up an example, the programmer might write it so that every time the random number one shows up, the reel shows a jackpot symbol; with numbers two, three or four, it shows a seven, with numbers five through nine, a triple bar, and so on. The possibilities are programmed, but when they turn up is random, just as it’s random when a 17 turns up in roulette.

After a big win, the machine doesn’t go into makeup mode. Over a long period of time, normal results according to the odds of the game will yield a normal payback percentage, and your big win fades into statistical insignificance.

Just as when a table games designer sets the rules of a card, dice or wheel game, the slot programmer sets the possible outcomes, and the pay table gives you back a little less than the true odds of hitting the winners. You can hit several winners in a row, or none, for a number of spins. Results are random, but over hundreds of thousands of plays they will lead to something very close to the programmed payback percentage.

Programmed, yes. Random, yes. Just like any other casino game, but in an electronic sort of way.

Your choices do make a difference in pick’em-style bonus events, but not in any way you can predict or control. The programmer, on the other hand, knows that over a very long time, the bonus event will yield an average payback.

Let’s make up a simple bonus event, in which you pick one of three symbols to reveal a bonus award. If you touch one symbol, you get 25 credits, if you touch a different one, you get 50, and if you touch the other you get 75.

The amount you get isn’t predetermined. You will get the amount assigned to whichever symbol you pick. If you’re able to pick the 75-credit space, good for you.

However, no system for trying to determine which symbol hides the 75 will work. The shuffling of the symbols is random. The 75 could be on the left three times in a row, or not at all for several trials, or any other number. Over a very long time, hundreds of thousands of trials, players will pick the 75 about a third of the time, the 50 about a third of a time, and the 25 about a third of the time.

The odds of the game lead to an average payback of 50 credits on that particular bonus event. In determining a target payback percentage for the game, the programmer knows that, and that’s built into calculations.

Real-life bonus events have more possibilities and the math is more complex, but the principle is the same. Over time, an average win will emerge, and the programmer can build that into the targeted payback percentage.

“Random results” is not the same as saying “equal results.” A game doesn’t have to be programmed so that a jackpot symbol shows up as often as a blank space, or a bonus symbol as often as a cherry.

The odds of the game are set so that blank spaces will show up more often than winning symbols and small winners will show up more often than big winners. On three-reel slots, that will lead to there being more losing spins than winners, and on five-reel video games it will lead to more “wins” for amounts less than the size of your bet than bigger winners. The programmer sets the odds of the game, and then lets random chance take its course.

When you play, may the chance be with you.

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