Re: [Phys-l] Symbol for uncertainty

[William Robertson <wrobert9@ix.netcom.com>]

Got it. I learned just delta.

Bill



On May 13, 2011, at 7:42 PM, James McLean wrote:

> Yes.  It cannot serve the purpose that I am referring to.
>
> +- notation is just fine for reporting the result of a measurement.
> That's what I mean by "One can get a long way without using any
> particular symbol."
>
> However, suppose that you want to teach that when physical variables  
> are
> related by x=z+y, if you measure z and y, then
> del-x = sqrt((del-z)^2+(del-y)^2).
> As far as I can see, to teach this it is nearly a absolute requirement
> to have an algebraic symbol that represents "uncertainty in z" (which
> I've here written as del-z).  The +- notation is no help at all.
>
> To put another way, I am NOT asking about how people like to notate
> uncertainty of a specific measurement.  After all, that tradition is
> very firmly established.  I AM asking about what people use for an
> abstract algebraic symbol for uncertainty, when the need arises.
>
> Cheers,
> -- James
>
> On 5/11/11 4:47 PM, William Robertson wrote:
> > I notice on your URL that there is no choice for a simple +-  
> > notation.
> > Is there any reason to be dissatisfied with that?
> >
> > Bill
> >
> >
> >
> > On May 10, 2011, at 8:19 PM, James McLean wrote:
> >
> > > Hi all,
> > >
> > > I'm curious about what symbol everyone here uses for uncertainty in
> > > measurement.  One can get a long way without using any particular
> > > symbol, but in some situations (e.g., teaching about uncertainty
> > > propagation) you need an algebraic symbol to represent the
> > > uncertainty,
> > > separate from the measured value.
> > >
> > > * Many at my college use capital-delta-x (for variable x).  I prefer
> > > to
> > > avoid that because the same symbol is used for "change in x".
> > > * Some like to use sigma-sub-x.  But the way I read things, that
> > > really
> > > should be reserved specifically for standard deviation.  Some
> > > uncertainties aren't standard deviations.
> > > * NIST recommends u(x), but I don't particularly like that because  
> > > it
> > > looks like a functional relationship.
> > >
> > > So let the masses speak!  I've set up a survey at the URL
> > > <http://survey.geneseo.edu:8080/survey/entry.jsp?id=1305076116174>
> > > Go there to register your preference!  When the votes stop rolling  
> > > in,
> > > I'll report on the results.
> > >
> > > Cheers,
> > > -- James
> > > --
> > > Dr. James McLean                     phone: (585) 245-5897
> > > Dept. of Physics and Astronomy       FAX:   (585) 245-5116
> > > SUNY Geneseo                         email: mclean@geneseo.edu
> > > 1 College Circle                     web: http://www.geneseo.edu/~mclean
> > > Geneseo, NY  14454-1401
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