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

Bob Camp kb8tq at n1k.org
Sat Oct 25 18:54:34 UTC 2014


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)…

Bob

> 
> Cheers,
> Magnus
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