how they set slot machine odds

I’ve asked The Master, I’ve checked the archives, and now I turn to the masses, hoping for edification. How do they set the odds in slot machines? Particularly the ones with rotating drums. Can they determine that some pictures will come up less than a random chance number of times? And what about the poker machines? They say that the game is played with a 52 card deck. How do they see to it that certain hands don’t come up very often. I mean, how can it be that some casinos have “looser slots” than others? or different payoffs? How do they do that?

In modern slot machines, when you pull the machine arm (or press the button), a random number generator picks numbers, with each number corresponding to a specific stop on a reel. The machine then stops each reel at the proper place based on what numbers popped out of the generator. To set the odds, the house weights each stop on each reel. I would imagine that the weighting algorithms vary by machine, but one simple method would be for the generator to pick a number from a large pool of numbers, and have the possible outcomes map to reel stops in various proportions. For instance, if a reel had 20 stops, you could generate a number between 1 and 100, with 1-10 corresponding to stop 1, 10-15 corresponding to stop 2, etc… This way, you could set the probability of the various combinations appearing on the reels, and set payouts accordingly.

As for video poker, I don’t believe there is any special weighting involved. There’s no need to go out of your way to ensure that, say, a royal flush will pop up infrequently since the hand is unlikely to pop up in the first place. To ensure that the house makes money, all it has to do is set the payouts on the video poker machines such that the payouts are slightly lower than the odds for achieving particular hands (as an example, if a hand has a 1-in-10 chance of showing up, setting the payout to 9-to-1 for that hand would ensure that the house made money).

For the slot machines;

depends on how often the image is placed on the barrel.

Picture a hypothetical three sided barrel.

Two sides with cherries and one with a lemon.

There are a total of three columns.

3^3 = 27 total possible combinations.

222 = 8 possible ways to get a cherry

111 = 1 possible way to get a lemon.

9 total possible ways to win.

9 / 27 overall odds (one out of three) of winning.

8/27 of getting a cherry. 1/27 of getting a lemon.

It has been, err, 5 or so year since I last did anything with statistics though, so these may not be the right numbers, but the overall idea is there.

The number of times a symbol is placed on the barrel varies.

Of course most slot machines are digital now days any ways so. . . . :slight_smile: Just a lines of computer code anyway.

As for poker;

pure math stats. What is figured is the total possible ways that that hand combination could EVER come up.

52 cards, 5 cards at a time, errr.

Fudge.

311,875,200 total possible combinations I think but do not quote me on that, I think it is 5251504948 but as I said, it has been awhile.

Any ways. There are, err, 2 possible combinations to get a pair for each card type, 13 types of cards,

hmm let me check this for a second

2D,2C,2S,2H

2D2C
2D2S
2D2H
2C2S
2C2H
2S2H

Ok six ways to get a pair for each type of card, 13 types of cards.

78 ways to get a pair.

Err.

I think.

Ok I give up, I have done this proof before, of the probability for each possible hand in poker, but apparently I cannot do it anymore.

::walks away in shame::

Com2Kid: Sorry, but even the ‘mechanical’ slots are all computer driven these days. The reels are connected to stepper motors and are totally under the computer’s control. So the outcome of the spin is determined before the reels even start to move.

Oh, and have you ever seen someone go ballistic because they walked away from a machine and it ‘paid off’ on the next spin? They shouldn’t have worried, because if they had stayed there it probably wouldn’t have paid off for them. Not because of any chicanery, but because the RNG inside the slot runs all the time, and when you push the button or pull the wheel it grabs the next value and uses that to determine the outcome. So if you had stayed at the machine yourself but pulled the handle even a millisecond later than the other person, you wouldn’t have achieved the same outcome.

It’s sad to see so many people addicted to slot machines because they believe in fallacious concepts. Windsor casino actually had to make ‘reserve’ signs available to slot players who were terrified to leave their machines for fear that they were about to pay off. As a result, people were actually urinating between the slot machines because they wouldn’t go to the bathroom.

And even with the old slots, it wasn’t quite as easy as you describe. Because the reels were designed so that the distribution was non-uniform. In that way, the machine could be set up to deliver some combinations more often than others. And often, the ‘common’ combinations would be set up so that the big jackpots were just one spot away, to make the player think he came close.

The same technique is used in promotions where you have to collect all the letters in a word or match some other pattern. They’ll ship 100,000 copies of every letter except one, which might only have 10 or 20 copies in existence. So lots and lots of people will be only one letter away from the big jackpot, but in reality the odds of winning were completely dependent on whether or not you had that single number, so matching all the rest was almost irrelevant.