In a modern slot machine, the odds of hitting a particular
symbol or combination of symbols depends on how the
virtual reel is set up. As we saw in the last section,
each stop on the actual reel may correspond to more
than one stop on the virtual reel. Simply put, the
odds of hitting a particular image on the actual reel
depend on how many virtual stops correspond to the
actual stop.
In a typical weighted slot machine, the top jackpot
stop (the one with the highest-paying jackpot image)
for each reel corresponds to only one virtual stop.
This means that the chance of hitting the jackpot
image on one reel is 1 in 64. If all of the reels
are set up the same way, the chances of hitting the
jackpot image on all three reels is 1 in 643, or 262,144.
For machines with a bigger jackpot, the virtual reel
may have many more stops. This decreases the odds
of winning that jackpot considerably.
The losing blank stops above and below the jackpot
image may correspond to more virtual stops than other
images. Consequently, a player is most likely to hit
the blank stops right next to the winning stop. This
creates the impression that they "just missed"
the jackpot, which encourages them to keep gambling,
even though the proximity of the actual stops is inconsequential.
A machine's program is carefully designed and tested
to achieve a certain payback percentage. The payback
percentage is the percentage of the money that is
put in that is eventually paid out to the player.
With a payback percentage of 90, for example, the
casino would take about 10 percent of all money put
into the slot machine and give away the other 90 percent.
With any payback percentage under a 100 (and they're
all under 100), the casino wins over time.
In most gambling jurisdictions, the law requires
that payback percentages be above a certain level
(usually somewhere around 75 percent). The payback
percentage in most casino machines is much higher
than the minimum -- often in the 90- to 97-percent
range. Casinos don't want their machines to be a lot
tighter than their competitors' machines or the players
will take their business elsewhere.
The odds for a particular slot machine are built
into the program on the machine's computer chip. In
most cases, the casino cannot change the odds on a
machine without replacing this chip. Despite popular
opinion, there is no way for the casino to instantly
"tighten up" a machine.
Machines don't loosen up on their own either. That
is, they aren't more likely to pay the longer you
play. Since the computer always pulls up new random
numbers, you have exactly the same chance of hitting
the jackpot every single time you pull the handle.
The idea that a machine can be "ready to pay"
is all in the player's head, at least in the standard
system.
In casinos today, gamblers will find a wide variety
of slot-machine designs. In the next section, we'll
look at some variations on the standard game.
Extracted from "How Slot Machines
Work", HowStuffWorks (http://www.howstuffworks.com),
by Tom Harris. HowStuffWorks, Inc., 2005.
