Sample Size?

[RiverMise]

OK, this is sort of a math/stats question but I was wondering if any of your geniuses out there could shed some light. Lets say I am playing a game against the same set of opponents for some number of hands. How many hands do you think it would take before you could say something meaningful about your EV in the game? In otherwords, after how many hands can I safely say I can beat a game for XBB/100?

Thanks,
RiverMise.