[time-nuts] Changing ADEV, (was Phase, One edge or two?)

Magnus Danielson magnus at rubidium.dyndns.org
Sat Oct 25 16:08:42 EDT 2014


On 10/25/2014 08:54 PM, Bob Camp wrote:
> Hi
>> On Oct 25, 2014, at 2:18 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>> On 10/25/2014 07:06 PM, Tom Van Baak wrote:
>>>> In the case of the TimePod, the data can be presented when you have *very* few samples to work with.
>>>> That said, it is interesting to watch it bring up error bars (which are indeed correctly calculated)
>>>> and then see the trace walk outside those error bars as the run progresses.
>>>> There are other measurements that are a bit less susceptible to this.
>>>> None of them have any magic to get around sqrt(N).
>>>> Bob
>>> Maybe I don't understand error bars. For a dynamic display like TimeLab, walking outside (1 sigma) error bars is expected about 1/3 of the time, no?
>> Error bars works a little differently, as they indicate with some probability (say 1-sigma) within which range the real value is.
>> By the way, sqrt(N) is not very accurate estimator.
> But it is a common way to express the fact that your data is unlikely to converge any faster than sqrt(N)…

Yes, but it gives you false hope of how quickly it really converged, as 
the cross-correlations make you converge even slower than sqrt(N).


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