[time-nuts] Changing ADEV, (was Phase, One edge or two?)
Bob Camp
kb8tq at n1k.org
Sat Oct 25 17:45:08 EDT 2014
Hi
> On Oct 25, 2014, at 4:08 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>
> Bob,
>
> 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).
Except that management would really like it to converge as N …
Bob
>
> Cheers,
> Magnus
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