[BruceZ]

Actually irchans answered what was going to be my next question (how long before you can "accurately" estimate your win rate).

Notice that you get irchans' numbers from what I said above. If your hourly standard deviation is 10 times your hourly rate, say hourly rate = 1 bb/hr and hourly standard deviation = 10 bb, then if you play 100 hours you divide 10 by sqrt(100) = 10 to get 1. This means that the standard deviation of your hourly rate will be 1 big bet after this amount of time, or that your true hourly rate will be +/- 1 big bet from your actual hourly rate 68% of the time as I explained. After 400 hours it would be within 10/sqrt(400) = 10/20 = 1/2 big bet or 1 small bet. Notice that it will take even longer than this if your standard deviation is greater than 10 times your hourly rate. This standard deviation of your hourly rate is actually called the "standard error" of the hourly rate. It is a measure of how accurate your estimate of your hourly rate is. Note that it takes a very long time to have a very accurate estimate of your hourly rate. If you want the standard error to be 10%, you would have to play 10,000 hours, since 10/sqrt(10,000) = 10/100 = 10%. Note that this doesn't mean you really know what it is to within 10%, just that it will lie within 10% 68% of the time (68% confidence). 95% of the time it will lie within twice this or 20% etc. Note that it takes much less time for your standard deviation to become accurate than for your hourly rate to become accurate.