This "question" is really two seperate questions:

1) What is the standard deviation for a typical winning limit hold-em player at middle limits? I have heard 10, 15 and 20 BB, so would anyone like to clarify?

2) Thinking back to my statistics classes I remembered this line, "The variance/mean of a sum of independent random variables is the sum of the individual variances/means." Now my question: would this theorem apply to multi-tabling? To elaborate, say I have a u=1/hr (mean) and a var=225/hr per table, and consequently a std. dev.=15/hr. Does that imply that two-tabling I would have a u=2/hr, var=450/hr, and std. dev.=21.21/hr? Thanks all.