For teaching boxplots, I give students Darwin's cross vs. self polenated plant data, and get them to try to determine the difference using histograms. Then show them using boxplots.
there have been several comments that cast a negative tone on histograms ... when compared with boxplots ... that i feel are a bit misplaced
histograms are a perfectly legitimate way of looking at frequency data ... just like dotplots ... frequency polygons ...
BUT, they were not designed to report on the median (though sometimes you can find it), nor the quartiles (though sometimes you can find them) ... nor have specific designations for operationally defined "outliers"
while a boxplot does give this additional information ... what it does NOT give you information on in any "reliable" way is the SHAPE of the distribution ... if that is important ... then a boxplot will not really lead you toward your answer
which brings me to my "request" of minitab (or any software company) ... made several times ... to develop what i call a DOXPLOT ... which shows the dotplot (could be a histogram) ... and on the baseline has some sort of special tick marks for Q1, Q2, and Q3 ...
GO DOXPLOTS! would combine the good features of both histograms/dotplots/frequency polygons AND boxplots ...
as for the designation of outliers ... this is a totally arbitrary designation ... which in some cases may be of value ... and in other cases (probably most) is probably a misnomer and, w/o much value
a rough sample DOXPLOT might be (something like):
: : . . . : . : : : : . : : : : . : : : : : . . : : : : : : : : : : : : : : : : : : : : : : : . : : : : : : : : : : : : . : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : ---+---------+---------+---------+---------+---------+---C1 20.0 24.0 28.0 32.0 36.0 40.0 Q1 M Q3
---------------------------------------------------------- Dennis Roberts Email: [EMAIL PROTECTED] Web: http://www.personal.psu.edu/users/d/m/dmr/droberts.htm
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