While most people play slot machines for fun it is still good to know how slots paybacks are determined.
Slot machines odds are determined by payback percentage. If a machine has a 90% payback that means the house has a 10% edge. For the fiscal year that means the machine will payout 95% of what it takes in, leaving the other 5% for the casino.
One thing to remember is slot machine payout percentage goes up and down throughout the year. Even if the machine has 95% payback it will not pay out as the same rate constantly. The machine can pay out over 100% and at other times 50%. You just have to try to catch the machine when it is in paying out at a high percentage and know when to quit.