Hi Scott,
Is this the most recent IXAS report on error reporting standards?
http://www.i-x-s.org/OLD/subcommittee_reports/sc/err-rep.pdf
Yes. To be clear, the main value of reduced chi-square is that it can
be used (even if with some inherent uncertainty) to compare two models
with different
Hi all, I see that the reports of the fits a perform in arthemis have Chi
really big. The fit is really good and the Chi should be closer to 1 than to
100.
The problem, is what should I report as the Chi. Uncertain in delr or
ss have the same problem, are big like the results.
I found the topic in
Hi euG,
I don't report chi-square at all. I know that the official IXS reports
suggest it, but until the question of what to use for the measurement
uncertainty is adequately addressed within the community, it seems to
me that the number is not very meaningful in an absolute sense. It is
Hi Scott,
here I copy a part of the report:
Independent points = 6.222656250
Number of variables = 4.0
Chi-square = 247.145092496
Reduced Chi-square = 111.193574128
R-factor= 0.017422216
Guess
Hi euG,
That amp is not physically reasonable, unless you're using it as a
proxy for the coordination number.
The uncertainty on the other variables does not seem high to me for a
single-shell fit. Well, 2 eV is a bit high for an uncertainty on E0,
but not crazy high.
There are some
Hi Scott,
I forget the amp, I left the N =1, that is the mistake, sorry I have de S02
from other oxide to transfer it.
I found that error bars in Ifeffit are scaled by Chi2 reduced, so should I
transform the error or inform them directly as reported?
Regards, euG
Report the error bars as given; otherwise you're reintroducing the
unknown measurement uncertainty factor. Then somewhere in your paper
cite ifeffit and make clear that you used that method to determine
uncertainties.
--Scott Calvin
Sarah Lawrence College
On Aug 18, 2009, at 7:31 PM,
Hi Scott,
Thanks for you help.
Best Regards, euG
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