[Ifeffit] statistical parameters

Stefano Ciurli stefano.ciurli at unibo.it
Wed Dec 14 11:16:21 CST 2005


>According to what you said above, Nvar = 7, so nu=24.83, which is much
>closer to 23.54.

of course. My mistake. But still...

>That still seems bigger than rounding errors, though.

that's what I am saying...

>Here is my understanding of Ifeffit, but I am sure Matt can elaborate.
>Background removal uses the integer part of dk*dr*2/pi+1 to determine
>the number of knots.  Fitting uses dk*dr*2/pi as a real number to
>determine Nidp.  In any case, that's what Artemis reports when you ask
>it how many independent points in a project.  My memory is that I
>checked it against Ifeffit's report of Nidp.

Not sure I fully follow, as I am not talking about background 
removal, but in any case, shouldn't the ratio between chi^2 and 
reduced-chi^2 be an integer number, whichever? Plus, I have found a 
few documents in which Matt reports Nidp as 2dkdr/pi, some others in 
which he reports 2dkdr/pi+1. In SK's thesis, which is available on 
the net (thanks Shelly :-)) she says +2. I was simply wondering which 
is the right formula used in IFEFFIT, and if it is different from 
what reported in Stern, Phys. Rev. B, 1993, 48, 9825-9827, why it is 


Stefano Ciurli
Professor of Chemistry
Laboratory of Bioinorganic Chemistry
Department of Agro-Environmental Science and Technology
University of Bologna
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