Originally Posted by koolmoe
It really depends on your variance. You are trying to determine a distribution of your win rate rather than a fixed number (which is why you report both numbers). There is no single number that tells the whole story.
Because of this, you need the sample variance to converge. The sample variance for a large number of samples from a normal distribution is close to 2*SD^4/N where SD is the true standard deviation and N is the number of samples, i.e., 100 hand chunks you have played. For your sample SD of 35, it suggests that you need to play 10,000,000 or so hands to get decent convergence on the sample variance. I suspect your sample variance will come down a bit as you play more hands. If your true variance is closer to 20, for example, then you'd be relatively certain of it's value after only 1,000,000 hands. At a SD of 10, you'd only need maybe a couple of hundred thousand hands.