Frank von Delft wrote:
(I'm probably wrong, but I want someone to show me,and not with
hand-waving
arguments or invocation of crystallographic intuition or such)
To convince me, someone needs to show that the expected value of the
change
in |Fo-Fc| at a test reflection upon a change in the model (a step of
refinement)
is negative, even in the absence of any real improvement in the model,
simply because the change reduces |Fo-Fc| at a sym-related working
reflection.
The problem is that a) the statistical drift will be very small, and b)
If you can show me it is negative, I don't care how small.
But if it would amount to a change of 0.001 in R-free I'm
not going to worry too much about it!
(Can you describe this "statistical drift" a little better?)
that this will be for *almost every* reflection in the test set. If it
were just a few, you'd be right, but not when it's all of them: then
your Rfree will not be informative.
I don't get that- if the expected value is zero for each reflection,
then the more you average the better it will approximate zero.
That's in the absence of NCS restraints. In their presence, it's bad
anyway, because you're forcing Fc to be (almost) equal for both
reflections.
For now I'm not arguing about that.
phx.
