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RE: st: RE: Error Bars on Histogram or Bar Plots


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Error Bars on Histogram or Bar Plots
Date   Mon, 2 Jun 2003 16:58:08 +0100

Buzz Burhans

> >3. How error bars should be shown
> >=================================
> >
> >I think there's a wider issue here about one
> >kind of graph which I think Buzz has in mind.
> >My impression is that it is very common
> >in some (biological?) sciences but much less so
> >in mainstream statistical literature. This
> >graph shows magnitudes by thick bars with
> >bases at 0 and errors by thin bars centred
> >at the top of the bar, schematically
> >multiples of
>
> Yes, I am referring to biological sciences literature. I am
> not sure
> whether what you have depicted is what I am referring to or
> not.  If it is,
> I would have to say the reaction of the users group was
> unfortunate,
> because the represention of error bars is common, in fact
> standard, in many
> instances. There are many mainstream biological sciences
> journals that use
> similar graphic representation of error terms. It is so
> mainstream I
> question the need to argue about it or defend it. It is an
> integral part of
> representing much data that is published. And while your
> example represent
> one use, such bars are also important in interpreting
> connected line plots
> as well.
>
> I encourage Stata Corp to correct what is, in my opinion, a
> substantive
> deficiency in their fine graphics capabilities. In doing
> so, I would again
> refer them to XTGRAPH as an excellent example of related functional
> concerns, as I outlined previously(flexibility, integration
> with models,
> etc.). There are other user written plots that construct
> error bars, I
> know, and I assume these were also driven by some perceived
> need for error
> bars. I just don't think this is something that should be
> relegated to user
> written functionality...it should be, in my opinion, a
> integral part of the
> graphical capability of Stata.
>
> Bottom line, the representation by error bars is, in my opinion, an
> important, informative, and necessary component of
> graphical representation
> of data in many (obviously not all) cases.  Any statistical
> graphics
> program that fails to accomodate this is deficient, again,
> my opinion.
>
> I think, Nick, we are mostly in agreement.

Agreed that we agree, mostly. But the premise that "lots of
people do this, so it is not discussable" is not one I sign
up to. Lots of people use pie charts, but when I can I try
to persuade audiences that it's a usually a bad idea. And
in this detail, and almost all others to do with graphics,
I stand on the shoulders of giants.

More pertinently, I gave three specific arguments
against this kind of error bar. I await counter-arguments.

Also, in fairness to my colleagues at the users' meeting,
I should stress that there were reasons for their reactions.

Nick
n.j.cox@durham.ac.uk

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