Probability and Slots – How to Win Big and Lose Small


In the movie National Lampoon’s Vegas Vacation, Chevy Chase’s character suffers from gambling fever in an attempt to beat his losing streak. In real casinos, the house edge keeps gamblers from abandoning the tables and walking away from the slots. But if you understand probability, you can develop a strategy that’ll keep you from going broke.

The term “slot” can mean different things, but most of the time it refers to a machine that accepts cash or paper tickets with barcodes. Those tickets are then scanned and the machine credited according to a pay table, which lists how many credits you get for matching symbols on a single reel.

When manufacturers design a slot, they must consider the number of possible combinations on each reel, and how those symbols might appear in groups or in rows across multiple reels. These factors determine how much a game will return to the player, known as its payback percentage. You can see this on PAR sheets, and anyone with a calculator and reasonable math skills can calculate it. Bonus rounds complicate the formula, but they’re still based on randomness.

Another factor is a slot’s volatility, which affects how often it pays out. A low variance slot pays out smaller wins frequently, while a high-variance slot may not pay out for long periods of time, but when it does, the winnings are large. A third element is a slot’s jackpot, which is the maximum amount of money that can be won on one spin.