[Ifeffit] Reduced chi square values versus F-tests for second shell fits
mgs at udel.edu
Thu Mar 21 16:38:22 CDT 2013
Thanks for your response. By “second shell fits” I mean that the best values for the first shell
were fitted then fixed and then the fitting R-range was moved to the second
shell. Similarly to how Matt Newville
He describes this as an acceptable approach, although, others in
the thread disagree.
Essentially, my question is why
do the F-test and the RCS results not agree with each other? The F-test indicates model 2 may not be a
statistical improvement over model 1 while the RCS values show that model 2 is
definitely an improvement over model 1. If I consider a reduction in the RCS value of >2x as significant,
then I would pick model 2.
However, can I apply this logic when fitting the second shell with
the best parameters for the first shell fixed and the R-ranges over the second
Thank you again,
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