Understanding Probability and Odds

The terms ‘probability’ and ‘odds’ are two common ways used to describe how likely it is that a certain event will happen. In gambling, both terms tell you how likely you are to win, but they will do this in different ways.

* Probability is the number of winning outcomes divided by the total number of possible outcome.
* Odds compare the number of losing outcomes to the number of winning outcome, in ratio form

Think of rolling a dice and hoping for a number 4 to come up. In this case there are 6 possible outcomes, 1 winning outcome and 5 losing outcomes. The probability of rolling a number 4 would be 1/6 or 1 in 6. The odds of rolling a number 4 would be shown as 5 to 1

The maths of poker machines is simply an extension of this. Each reel has a number of symbols. The number of symbols depends upon the game, its paytable and its return to player. The reels also have different numbers of symbols e.g. reel 1 may have 32 symbols but reel 2 may have 39 symbols and reel 5 may have 40 symbols.

Also, symbols often appear more than once on a reel and this changes the likelihood of that symbol being selected.

If we go back to our dice and it has tow number 4s on it instead of only one, the probability of rolling a number 4 would change to 2/6. That is, it would become more likely than if there was only one number 4.