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Topic: Box&Whisker Plots/ Five Number Summary
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Rudy Wiegand

Posts: 18
Registered: 12/6/04
Box&Whisker Plots/ Five Number Summary
Posted: Oct 2, 1996 8:30 PM
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In reviewing several texts, I find that some use the Q1 & Q3 points in the
five number summary, while others use the upper/lower hinge points. A
cursory check makes it appear that these points are probably identical
except when n mod 4 =3 with n the number of data points. The TI-82 uses the
Q1 & Q3 points in its Box & Whisker plot, I would guess this is a TI
standard approach. Finally some computer programs use a linear
approximation to the quartiles.

One point of interest is whether students will be required to use a specific
method on the exam. A second point is whether they would be expected to use
the quick box plot, or the full box plot with identification and marking of

To this point, despite the fact that my text uses hinge points, I have
chosen to use the quartiles for the box plot and have recommended to my
students that the quick box plot is a quick-and-dirty approach with
appropriate consideration given to whether the plot suggests further
examination via the full plot.

Finally, I have spent two (45 minute periods)days in having the students
calculating variance using only the lists available on the TI-82 so that
they will understand how it is calculated and in particular the terminology
applied to Mean Squared Deviation. Once I am confident they understand the
methodology, and terminology they will be using the TI-82 values directly.
I should remark that the first third of this course is NOT being considered
AP level at our school. The idea was to attract as many good (not
necessarily great) students as possible to provide an introduction to at
least part of the field with the hope that many would remain for the AP

In any case, I have three questions concerning the exam:
(1) Will the 5 number summary use quartiles?
(2) If a Box & Whisker is requested, can we safely assume it is intended
to be the quick box?
(3) Is it likely that a student will be requested to find a variance
without access to the calculator?

Thanks for any information.

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