Video poker games, which have elements of skill, often return more to players than other slot. Each game, Ambrose says, has a set hold percentage and a pay table that details how often and how much games will pay back. Pressing spin activates the random number generator, which is an algorithm that determines whether each spin is a win or a loss, and how big a win is. So how do slot machines decide who wins and who loses? “Payouts on slots are statistically calculated,” says Ambrose. What’s left after the machine pays out its jackpots is the casino win, also known as revenue.

How can a player bet more money than she puts in? Well, if she puts in $100, wins a $50 jackpot, and keeps on playing until all her money is gone (including that $50 'win'), she has generated a drop of $100 and handle of $150. Another number you might hear is handle, which Ambrose defines as the total amount bet by a player. That is the money deposited by the player in the machines. When casinos look at how a slot machine is performing, the most basic number they look at is the drop. “It is all,” he says, “about the game math.”

To explain why they are so reliable for casinos, I talked to Bob Ambrose, who broke into the industry at the Tropicana Atlantic City in the early 1980s and is today a gaming consultant and casino management instructor at Fairleigh Dickinson University. Slot machines appeal to casinos because they are, as long as enough people play them, stable money-makers.

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