[Shillx]

The p-value on $11 ROI not= $22 ROI is .007 if you use an SD of 1.6 buy-ins. It would be pretty tough to blame varience for the the difference in results. So now you have to determine if the players are better or if your play has fallen down some. There is always some chance (about 140:1) that you were running very well and are now running very bad, but you look to be better off evaluating your game and sticking to the $11's.

Edited to say that this doesn't mean that your true ROI is -4% or whatever. It just means that either the 22's are harder then the 11's or your play has changed a significant amount.