Re: [Ifeffit] Two analysts, one spectrum, similar outcome?

Hi Mike: What I mean by "what question you are trying to answer" is that if you are interested in a specific fitting parameter, you might wish to make some assumptions and put constraints on other parameters so that you can extract the trend that you are interested in. Carlo On Tue, 13 Aug 2019, Mike Massey wrote:

It is true that we both have background information regarding the samples, and similar goals in terms of the questions we are looking to answer.

"You also need to think about what question you are trying to answer. If you have a specific goal in mind, then you may choose a different model than the individual who is seeking the answer to a different question."

This is, somewhat, the issue we are grappling with. A reasonable EXAFS fit is one interpretation of the data, but we are trying to find a way to deal with the problem of seeing what one wants to see in EXAFS data. To me, it's a bit of a problem, anyway. A version of "confirmation bias," I suppose.

The hope is that, if two of us independently reach a similar conclusion, we can have more confidence in the findings, perhaps?

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On Aug 13, 2019, at 7:59 PM, Carlo Segre wrote:

The answer you get will depend somewhat on the assumptions you make. if you are truly provided with data and no other information about the sample, then the job is challenging. If you know something about the sample that can help you start in a particular direction then the two analyses have a better chance of converging but it still depends on how you decide to approach the structural model.

You also need to think about what question you are trying to answer. If you have a specific goal in mind, then you may choose a different model than the individual who is seeking the answer to a different question.

The most likely way to approach this problem is to both have the same background information about the sample(s) and to mutually determine what question you are trying to answer.

Cheers,

Carlo

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On Tue, 13 Aug 2019, Mike Massey wrote:

I'm the dumb one. But it's an interesting question, and gets perhaps to the heart of the issue: to what extent does the smartness of the analyst, or their experience, or the fitting procedures used, or a butterfly flapping its wings in Micronesia, impact the results?

For the sake of argument, can two equally smart and experienced analysts working on fitting the same EXAFS spectra be expected to reach similar conclusions? I guess we'll find out.

Another colleague once said something like, "EXAFS is great: you publish a paper, then later you publish another paper re-analyzing the same data." Of course, he's a strictly computational guy, so I'm not sure he necessarily has standing to criticize...(Good-natured sarcasm font...)

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On Aug 13, 2019, at 6:43 PM, Anatoly Frenkel wrote:

Are they equally smart?

Anatoly

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On Aug 13, 2019, at 9:39 PM, Mike Massey wrote:

Hi Everyone,

I'm curious, has anyone ever tried turning two analysts loose on the same unknown EXAFS spectrum to see if their fits come out with similar conclusions? If you have tried it, how did it work out? Were the conclusions indeed similar? If not, why not, and what did you end up doing about it?

I was talking with a colleague today about our plans for data analysis, and we settled on this approach (since there are two interested parties willing to try to fit a series of unknown EXAFS datasets).

The hope is, of course, that the two analysts will independently reach similar conclusions with similar fits and structural models, but to my mind that outcome is by no means guaranteed. Given the (presumably) wide variation in fitting customs and procedures, I can envision a scenario in which there are major differences.

This got me wondering, "Has anyone tried this?" So I thought I'd ask.

Your thoughts and experiences would be welcome. Thanks!

Mike Massey _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

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-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Directory, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit

-- Carlo U. Segre -- Duchossois Leadership Professor of Physics Directory, Center for Synchrotron Radiation Research and Instrumentation Illinois Institute of Technology Voice: 312.567.3498 Fax: 312.567.3494 segre@iit.edu http://phys.iit.edu/~segre segre@debian.org