On 4/29/08, TexasTeach2 wrote:
> In what industry are Box and Whisker Plots used? Other than doing
> them in college I never did them for data comparison when I worked
> in the private sector as an Accountant. Most people that you present
> data to normally see Line Plots, Bar Graphs or Pie (circle) Graphs.
Ooh! Ooh! (Raises hand) Ask me! Just two days ago I used
box-and-whiskers. A researcher friend gave 24 mice a certain dosage of
a medication, and measured how this affected a pathogen. A histogram
was quite informative. We saw a bell shaped pattern skewed slightly right.
However, altogether she had eleven dosage groups. She had printed 11
histograms. Even if the scales had been the same and on the same page,
these were hard to compare, hence her visit to me. By stacking 11
box-and-whiskers plots all on the same scale we could easily compare the
distributions of each group. We could even subdivide each group into
male and female and compared 22 distributions, all on a half page of
stacked box-and-whiskers plots. The virtue of box-and-whiskers comes
mainly in comparing distributions and secondarily in exhibiting
outliers by one definition of outliers.
I am against presenting box-and-whiskers before students have played a
lot with histograms and have gained appreciation of common "shapes" of
distributions. Then, when you present box and whiskers as an easier way
to compare distributions, students are all for that! Outside that
context, you're right, box-and-whiskers tend to be inferior to
histograms and other presentations of data. I'd rather junior high
students learn to read histograms, make decent histograms, and master
several other core statistical skills, so that later in say 11th grade
they can appreciate the use and limits of box-and-whiskers plots. Just
because a construction is easy does not mean we need to present it so
early.
The point of a graph is to give insight.
In that light, pie charts are an interesting application of fractions,
common, yet seriously abused. If two categories are about the same size,
it is hard to tell which category is bigger on a pie chart. An ordered
bar graph is clearer and easier to make. If there are many categories,
a pie chart is often cluttered with labels, and a simple table is more
informative.
I look forward to this thread excising more misplaced math topics! I
speculate that math history has a lot to teach us about the
prerequisites and placement of a topic in the curriculum. - GJ
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