Bruce, would you (and anybody else here who is very familiar with variance calculations) mind reading and commenting on this post:
http://forumserver.twoplustwo.com/showth...page=0&vc=1
Sorry, it's very long and verbose, and realizing why it had to be would require scanning through the rest of the ugliness in that thread (which is 10x worse as far as verbosity goes), but I'd appreciate it very much if you gave at least this one a gander.