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Re: [Phys-L] spinner data -- experimentation 101


On 2017/Sep/18, at 17:46, John Denker via Phys-l <phys-l@mail.phys-l.org> wrote:


For the period data, the residuals are here:
https://www.av8n.com/physics/img48/fidget-spinner-period-residuals.png <https://www.av8n.com/physics/img48/fidget-spinner-period-residuals.png>

There is an outside chance that the glitches are real, perhaps
due to grit in the bearings ... but I would be willing to bet
they are bogus, due to problems in the analysis, perhaps in
the FFT routine. This is why you want to record the raw
signal. Don't be in a hurry to do the FFT.


I don’t know what JD has done, as my residuals for both fits is:

http://cleyet.org/spinner/spinner%20w:resids.jpg

The corresponding plot (freq. wrt time) is here: http://cleyet.org/spinner/spinner.jpg


Note the diff Chisq’s. Not valid for goodness of fit, as the SD is assumed one. IIRC, one would need to spin many times combine the data, and determine sigma for each point. Thirty times woiuld be enuff?

bc too old?