Hi Bruce,
On Thu, Oct 2, 2008 at 4:12 PM, Bruce Ravel
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.
Does it? I thought it used data_uncertainty=1 unless the uncertainty was explicitly specified. Does Athena use a value determined from the sigma when merging data, or is something? Should I read the Users Guide more closely? --Matt