Paul Colby
Science Advisor
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A. Neumaier said:Measured positions of a moving car, or measured times or measured currents or measured temperatures or whatever else people measure are not constant either, and still people trust their single measurements. Except when the noise is so large that repetition is necessary. Only then statistics enters.
Like all things, it depends on what one is doing. I think you're conflating engineering measurement with measurement as it might be defined in an "ideal" case. In current theory measuring the position of a car (how is that defined exactly?) is a quantum mechanical problem, though, as you point out one may choose to forgo QM for expedience without too much error. QM is never far away from an actual measurement. One would use some form of measuring device like a camera or such which has pixels which have counting statistics which are QM in origin. So there is a Hamiltonian for the car and it's interaction with the electromagnetic field. All of this matters at some level, even for cars.