Hi Andrew, If you are fitting XANES spectra with standards, a large source of uncertainty can come from the representation of the standards in matching the species in the sample. Shelly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Andrew Sent: Thursday, October 02, 2008 3:49 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] What confidence limit is implied in the error bars forleast-squares fitting in Athena Hi everyone, 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? (I have done a PCA of the XANES, and XRDs of the samples and am pretty confident in the phases that I'm fitting). I greatly appreciate the help! Andrew Campos