Percentile and standard deviation

[Grendel]

Hey, I've got a question for you guys. Assuming you have an accurately measured winrate (in BB/100) and standard deviation:

If you sit down and play 100 hands, with a result of X BB, I have a good idea how to calculate what percentile ranking that is. For instance, if X=winrate, that's the 50th percentile. If X=winrate+1SD, that's the 84th percentile. My statistics background is quite rusty, but I remember there being a lookup table for this sort of calculation.

My question is if you sit down and play a number of hands other than 100, with a result of X BB, how do you calculate that percentile?

Purely hypothetically, say my winrate is 2.0 BB/100 and my SD is 15.0. Now say I play a 500-hand session and lose 80 BB. This is an unusual result, but well within the realm of possibility. My question is basically how unusual this is. Is it the bottom 2% of 500-hand sessions, or the bottom 10%?

And to think, I was a math major once... [img]/images/graemlins/blush.gif[/img]

Thanks in advance,
-Grendel