On Thursday 02 October 2008 16:49:27 Andrew wrote:
I'm fitting data with the least-squares method in Athena and am not sure what the error bars correspond to. What I mean, are these 95% confidence limits, or is it some other statistical way for error analysis? If Athena says the weight of one phase is 0.049 (0.003), what confidence are in the 0.003 error bar reported by Athena?
They are 1-sigma error bars, with the caveat that they assume that the only source of noise is statistical noise. Since an XAS experiment is (almost) never dominated by statistical noise, it's generally a very conservative (in the sense that it almost certainly understates the confidence) 1-sigma. The dominant source of error in a typical XAS experiment is often something like sample inhomogeneity. I am not really certain how to quantify that sort of thing, so I don't actually know how to report a better error bar. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/