Slot Machine Math

As we all know, to win on a slot machine is pure luck. Sometimes you win, most times you lose as one tries to get the best entertainment value for their money. However, I have come across a game that defies the math. For the sake of argument, here are the given conditions: a video slot with an approximate payback percentage of 91%, $50 minimum coin-in per play – maximum $120 producing 170 to 400 spins respectively, my personal winning percentage is 80% (more than 20 play dates). If one plays a similar video slot, then what would be the expected number of wins with 20 events?

You haven't given enough information. The number of sessions is irrelevant, since it could simply mask several small wins and a couple giant losses. Have you actually made money?

Yes ... but the money won is irrelevant. I am looking at this from a purely mathematical win/lose scenario. I bet a fixed amount on every spin and my play ranges between 170 to 400 spins per session. I know anything can happen in the short run but beating a certain type of video slot (not a specific machine) 80% of the time defies the laws of mathematics. What else is needed to calculate an expected number of wins? Thanks for the comment and question...

Based on my calculations, winning on a particular slot machine with a given standard deviation of 8.74% (the only SD on record) and a theoretical payout percentage of around 92% is .003 ... so this specific streak of luck is HIGHLY unlikely!