Simple question about standard deviation

[Fabian]

Assuming a win rate of 2BB/100 and a "typical" SD for 15/30 at party (what is a typical SD there btw?), how often in 10,000 hands should a 100BB downswing (or more) occur?

Thanks

[dogmeat]

You should have a SD of about 16 big bets per hour (you could have a terrible hour and lose $480) and maybe 18.5 big bets per 100 hands (again you could lose that, or have a great win of $555). To have a 100 big bet loss, you just need two crappy hours back to back. What are the odds of that, I don't know if my math is right for that - but I get a number of just under 4%. Is that right math gurus, or am I off by 100%?

Dogmeat /images/graemlins/spade.gif