Re: [Phys-l] Another uncertainties question...

[Bernard Cleyet <bernardcleyet@redshift.com>]

This reminds me of specification in mechanical drawings I've seen (and 
written), e.g.   2.010 " +0, -.002   Why not 2.009  +/- 0.001?  No 
idea.  In my case it musta been having written 2.010, not wanting to 
cross out after discovering what I later wanted, or 2.010 is ideal but 
no more and 2.008 is OK?????

bc very amateur mechanician

John Denker wrote:

> On 01/25/2008 10:36 AM, Jason Alferness wrote:
>
>  
>
> > Is there a standard accepted way to deal with non-detects?  
> >    
>
> The general rule is "say what you mean, and mean what you say".
>
> The rest is details.  The details are not particularly standardized.
>
>  
>
> > It seems not 
> > quite correct to do any of the following: Ignore it, call it zero, use 
> > the threshold detect value, 
> >    
>
> OK.
>
>  
>
> > or to use the threshold detect as the 
> > uncertainty for either.
> >    
>
> I assume the point is that the result is not "plus or minus"
> anything, because it can't extend to the "minus" side.
>
> The fancy way to report an asymmetric distribution is to
> give the nominal value "plus" something "minus" something
> else, as in 10 (plus 3, minus1) ... or in this case
> 0 (plus 3, minus 0).  I've seen that in plenty of official
> documents, so it must be fairly widely understood, at
> least among experts.  However in this application, it
> may be fancier than you need.
>
> It is always acceptable to spell it out in plan English:
>  none detected (threshold 3)
>  none detected (sensitivity 3)
>  below threshold (threshold 4, sensitivity 2)
>
> or whatever...............
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