# Finding the Uncertainty in a Spectral Line

Currently, I am doing a lab in school on atomic spectroscopy. After taking readings of strong emission lines of various elements, I have fit the data using a Voigt Profile function from lmfit. The function minimizes the reduced chi-squared and returns the best fit along with fitting parameter values (center, amplitude, sigma, gamma). I am mainly interested in the center of the line profile. But, what is the uncertainty in this reported center? Or how would I report the measurement and its uncertainty.

• This is really a question about statistics and not astronomy or even physics. – Carl Witthoft Dec 2 '19 at 15:01
• I'm voting to close this question as off-topic because it's a statistics question – Carl Witthoft Dec 2 '19 at 15:02
• @CarlWitthoft we can vote to close a question here if it is off-topic in this site, but "because it's an X question" or "is better asked elsewhere" are not good close reason. OP decides where they would like to ask it. However I'm sure that the OP would get an excellent answer in Cross Validated SE though they might be tougher on the question as written. – uhoh Dec 3 '19 at 2:20
• @ahayes24 have you looked at the out.fit_report() method shown in your linked documentation? Search for "+/-" I think that's what you are looking for. However, I am not sure that's the whole story because when strong correlations are present (those are also included in the fit_report) then a poor fit may have worse uncertainties than the +/- might suggest. Now that's a question for Cross Validated SE! – uhoh Dec 3 '19 at 2:25
• @CarlWitthoft Apologies for writing this question here. I assumed Astronomy had a lot of experience in spectral line fitting so I thought I would try it here. I can move it to the Cross Validated SE section and make my question clearer. – ahayes24 Dec 5 '19 at 0:03