isnt one standard deviation 68% or something? how can you "be sure it isnt just variance" with only 68% sureness?
You can expand it to more than one SD if you want. If you multiply your N0 by 4 you will get the number of hands you need to play in order to have a 95% chance of overcoming the variance. Here’s a discussion about how to use N0:
http://www.blackjackinfo.com/bb/showthread.php?p=28936#post28936
-Sonny-
sounds to me like you could be a major loser and still consider yourself a winner, although i dont really know what 2 standard deviations is