Hi Shelly, I am very interested in Andrew's question too, but I am to ignorant to fully understand your response. Could you please provide some more detail? For example, when you state "a large source of uncertainty can come from the representation of the standards in matching the species in the sample." do you mean that heterogeneities (as Bruce mentioned in his email) in the standards are propagated into the fits of the unknowns? Or instead do you mean that an inappropriate choice of standards can create unreliability in the fit? I would appreciate any details you can add to your repsonse. Thanks, Don On Thu, 2008-02-10 at 14:22 -0700, Kelly, Shelly wrote:
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
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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
_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Melting rocks today for a better tomorrow . . . Don R. Baker, Professor of Geochemistry, Earth and Planetary Sciences, McGill University, Montreal, QC CANADA phone: 1-514-398-7485