Thanks to DAve W0LEV and others for bring up the subject of error analysis and significant figures.
My own background is like Dave¡¯s; a physics degree in 1965. Our professor in senior labs was very big on
error analysis. It¡¯s a hard subject. I asked at our local hospital regarding uncertainty and error in lab tests.
I never got a good answer.
A friend of mine, an engineering professor, made a joke ¡. ¡°If you want to be absolutely certain about a measurement, only measure once.¡± Do I need to explain?
Chuck KF8TI
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On Jun 14, 2022, at 1:49 PM, Jim Lux <jim@...> wrote:
On 6/14/22 9:24 AM, W0LEV wrote:
Thank you, Jim!!!
Again, we are not running a metrology lab nor do our measurements approach
those of HP, R&S, Tek, and others. Something my PhD friends tell me is
that error analysis and assignment of error bars is no longer taught - not
even at CU/Boulder. I had a required course dedicated to that musing to
obtain my Physics degree some 50+ years ago at Michigan State U.
The students today have no idea how the error bar is established or even
what it truly indicates. Several of us have tried introducing our STEM
students at LTO (Little Thompson Observatory <starkids.org>) to the concept
of measurement errors and how they affect final outcomes. We usually get
wrinkled foreheads and "why".
Yes, 5 parts in E-5 is -86 dB. Yes, the HP 8753C noise floor can measure
below that. But, not our inexpensive NANOVNAs. Mine typically shows a
noise floor of -60 dB, depending on frequency and measurement type.
Again, thank you to those who put these VNAs at a reachable price in the
hands of us amateurs and those who want to learn the "fine points" of RF
engineering.
Never measure the temperature with more than one thermometer.
Never determine the time of day with more than one Cesium clock.
Never determine _________with more than one _________.
Dave - W?LEV
"sig figs" is taught in high school and undergrad.
If you do any sort of hard science classes they cover measurement uncertainties as part of the class (e.g. in lab) - Most lab classes discuss this (Undergrad chem lab certainly does).
The more sophisticated stuff is covered in classes like numerical analysis - if you're doing signal processing, for instance, round off and error propagation are a big thing. Same with classes on numerical solutions of differential equations, in connection with things like Runge-Kutta. I doubt there's many classes that specifically care about "calibration uncertainty" - you're on your own with mfr notes and the professional literature.
As a grad student, you'd be expected to get this knowledge in some way - there are a variety of short courses offered by various government labs as well as industry. For instance NIST has annual meeting in certain fields, and there's often some short courses associated with it.
