Introduction to Slot Machines

The slot machine consists of a 3-bar in blue, 2-bar in white and 1-bar which is in red.

When a bet is placed by pressing the spin button, the machine will select 3 random numbers, with each reel selected differently. These random numbers are chosen from a generator which randomly selects these numbers at a rate of thousands per second. The final outcome would be the numbers chosen when the play is initiated, which means that the result is pre-determined from the moment the spin is made. Conversely, in terms of the Red, White and Blue, each random number has 64 equally likely outcomes. A “Look-up Table” is set when each random number is mapped to a stop position. The following TABLE illustrates the Red White and Blue lookup table on the assumption that the total number of stops per symbol per reel.


 

As soon as the random numbers are chosen, they will be mapped to a stop on the machine using the Look-up Table where the outcome will be scored and player will be rewarded if he wins anything. For instance, if the random numbers chosen were 26, 8, and 43 the player would get Blue 7, Blank, Red 7. It should be noted that there will be clusters of the same symbol in a row. For example, stops at 60 to 62 on reel 1 are all mapped to a 1 bar symbol. These will be directed to the same 1 bar symbol on the actual reel. There are exactly 22 groups of like symbols on each reel, which is the standard number of stops on an electro-mechanical three-reel slot machine, known as a "Stepper Slot." In addition, there is only stop 45 on reel 1 mapped to the red 7 symbol. There will be 5 positions each on the blanks above and below it which often causes near miss effect when the reel stops directly above or below the highest paying symbol. The return of the machine can be calculated by summing up the number of position for each symbol on each reel to get the total symbol weightings. The following TABLE shows the summation of the total weights.


 

With the weighting of each symbol and reel known, it is easy to calculate the return. The following table shows the win, number of combinations, probability, and contribution to the return for all possible events. For example, the table above shows the number of white 7's are 6, 1, and 7, for reels 1, 2, and 3 respectively. The total number of winning combinations for three white sevens is thus 6 × 1 × 7 = 42.

 

The lower right cell shows a return of 86.58%. That means that for every dollar bet at the one coin level, the player will get back 86.58 cents, on average. Doing the same table for two coins results in a return of 86.58% as well, and three coins has a higher return of 87.47%, due to the disproportionately high win on the top two pays. The standard deviation is 9.03 for 1 or 2 coins, and 10.80 for 3 coins.