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Jon Peltier Jon Peltier is offline
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Default Creating notches in box whisker plots in Microsoft Excel

Gaj -

I'm not an entomologist, nor have I read much on the anthropology of
monkeys. I've worked in scientific research as a metallurgist (for my
doctorate and a dozen years of employment following that), and as an
engineer in manufacturing. Maybe not the widest mathematical background, and
I'm not degreed in statistics (though I've taken a graduate level course or
three). I've encountered thousands of box and whisker charts and their
variants, but I've never seen a notched box chart used in the heat of
battle.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
Peltier Technical Services, Inc. - http://PeltierTech.com
_______


"Gaj Vidmar" wrote in message
...
Duh, every now and then even proved experts (even with a degree in
statistics) say something that leaves me deeply perplexed.

Less than five minutes of googling reveals these five fine examples:

- Exhibit 1 (electronics / mobile phone manufacturing, 1996)
http://ieeexplore.ieee.org/iel3/4031...rnumber=561268

- Exhibit 2 (experimental / cognitive psychology, 1996)
http://faculty.washington.edu/jmiyam...f%20pref. pdf

- Exhibit 3 (physical anthropology / monkeys, 2002)
http://www.hopkinsmedicine.org/FAE/CBR2002AJPA.pdf

- Exhibit 4 (entomology / PhD thesis on honeybee parasites, 1994)
[I mean, I've published in truly numerous fields of medicine, psychology,
statistics, computer science, nuclear physics, physiotherapy, management,
phylosophy and more and what not, but is this topic exotic or what?!]
http://doc.rero.ch/lm.php?url=1000,4...se_RickliM.pdf

- Exhibit 5 (a physicist teaching maths presenting grade distribution at
an
exam, 2006/7)
[trust me from plenty of experience with such people that being a
physicist
and/or teaching mathematics otherwise tends to preclude knowledge and
understanding of statistics]
http://www.maths.qmul.ac.uk/~ob/MAS2...docs/stats.pdf

[if URLs are broken across lines, please put them together in your
browser]

Note that I've selected only freely downloadable publications, while from
an
academic institution with subscription to various online services from
major
scientific publishers there are literaly dozens more readily available
examples!

Of course, your definition of "real display of information" might exclude
any kind of scientific or even technical publication, thus meaning only
"business" stuff and the general press. (Though I sincerly hope that it is
not what you meant.) In that case, my objection should be disregarded.

Regards,

Gaj Vidmar, PhD
Univ. of Ljubljana, Fac. of Medicine, Inst. of Biomedical Informatics

"Jon Peltier" wrote in message
...
Del -

Your chart allows plenty of different quantities to be shown, but I

suspect
it may become cluttered, and at least for now, it's unfamiliar, and
forces

a
lot of back and forth between the chart and the legend. Don't knock a
"familiar idiom".

The box plot is pretty much self-explanatory especially since it is
familiar, and the difference between the box itself and the whiskers is
immediately recognizable (compared to your multiple error bars colored
different shades of gray, which is slower to be interpreted). If you
could
make whiskers of various line lengths, that might help.

I agree that the notched box plot must be rather obscure, as I've never

seen
it used in any real display of information.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
Peltier Technical Services, Inc. - http://PeltierTech.com
_______


"Del Cotter" wrote in message
...
On Fri, 15 Jun 2007, in microsoft.public.excel.charting,
Andy Pope said:
The technique describes how to use an xy-scatter to construct the
boxes.

You need to add a few more xy pairs in order to reduce the width of
the Median line and form the notches.

While I have as much reverence for the late John Tukey as the next
person, I don't see that boxes and whiskers as such are necessary these
days, except that they're a familiar idiom that the graph viewer will
usually recognise.

And even that isn't true for notched boxes, which I don't think many
people have seen. Certainly most couldn't interpret without them a
guide; I never even knew until reading that article just now what the
notches were supposed to represent-- I thought they were just meant to
enphasise the median in some way.

If we abandon the need to copy Tukey's shapes, doing this stuff in
Excel
immediately gets a lot easier. Here's my idea of a boxless "box" and
whisker distribution chart, with circled outliers and an error range
around the median, all just using the standard Excel symbol shapes.

http://i146.photobucket.com/albums/r264/del_c/
infographics/not_boxplot.gif

It would be simple to substitute circles, diamonds, or half-ticks, and
alter the thickness or colour of the Excel error bars, to suit your
preferences, and I think the point comes across even though they're not
the traditional boxes.

--
Del Cotter
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