The sheer number of possibilities makes the math that goes into slot machine odds more complicated than on table games. The number of winning combinations and the payoffs per winner work together to determine a game’s odds.
There also is an open field for game designers to assign how much each winning combination pays. There are thousands, and sometimes millions, of reel combinations.
Slot machine odds work in a similar fashion to the roulette example, except there are many more possibilities on the slots.