[andy800]

The outcome of each individual spin is random. The reason a slot machine is always profitable is due to the payouts. To put it simply, a result that will occur once every 100 spins only pays out 90 credits. The various PAR sheets allow casinos to adjust how much to tilt the odds in their favor. For the 1 in 100 example, the various pay tables might have that particular outcome pay 87, 89, 91 or 94 credits, allowing a casino to decide between 6% all the way up to 13% hold. But that particular combination of reels will still occur only 1 in 100 spins (theoretically, because it is in fact random, not cycling through a script).