[Ifeffit] Chi^2 and R-factor reporting requirements

[Stanislav Stoupin]

Hello all,

I would like to hear your opinion about reporting Chi^2 and R-factor
values in EXAFS studies.

I found that Chi^2 and R-factor values are not provided by many EXAFS
papers.
However, according to standards of The International XAFS Society
(http://ixs.iit.edu/) both these values should be reported.

My understanding is that the reduced Chi^2 should be close to 1 in ideal
case. In practice however, the value is always greater than 1 because of
systematic errors.
For example, my reduced Chi^2 values are around 300.
However, the R-factor values are about 3% which doesn't look as "ugly" as
Chi^2 reduced.

On the other hand, ifeffit overestimates uncertainties using reduced Chi^2
value. Thus, all errors are taken into account.
The final question: Is it appropriate to report just R-factor calculated
by ifeffit and the obtained uncertainties (which look reasonable) without
reporting the "ugly" Chi^2/reduced Chi^2 values?

Stanislav


Stanislav Stoupin
-----------------------------------
Research Assistant/PhD student
BCPS department
Illinois Institute of Technology

email: stousta at iit.edu
voice: 312-567-7983