[Ifeffit] statistical parameters

[Scott Calvin]

Hi Stefano,

Check out this paper:

H. J. Krappe and H. H. Rossner, Phys. Rev. B 61, 6595 (2000). 

The authors use a Bayesian analysis, and if I recall correctly, they
determine that the amount of actual information present is considerably
less than that given by the commonly used Nyquist criterion. That's because
the Nyquist criterion assumes "ideally packed" information, as if EXAFS was
a designed radio signal. Of course, the EXAFS gods had no particular reason
to send us information in that form, so the information content is somewhat
lower. To me, that makes the debate between +0, +1, and +2 somewhat
moot...lacking a better method, I generally figure I should avoid having
Nvar more than about 2/3 of Nidp, which is certainly satisfied in your
case. Personally, I use the +0 formula when reporting the number of
independent points, since it is the most conservative of the commonly used
choices.

--Scott Calvin
Sarah Lawrence College