Do slot payout %'s vary with the bet amount?

[adanthar]

My parents have a slot habit I've been slowly trying to wean them off of [img]/images/graemlins/tongue.gif[/img] In the meantime, however, I'd rather they at least play optimally.

Say a machine is advertised as a 95% payout. Betting 1 coin, the max jackpot is 500, 2 coins = 1000, but 3 coins (max) has a jackpot of 5,000. I understand a good chunk of the payout percentage comes from hitting the jackpot, so does this mean that betting less than the max results in lower EV?