How do you create box and whisker plots on a graphing calculator?

1 Answer
Alex Boroda
May 27, 2015

For a procedure similar to the graphing calculator, see this Plot.ly link . Please explore the Data tab, after reading the detailed explanation below.

Explanation . I never used graphing calculators, because in my country they are considered detrimental to actual mathematical reasoning. I know how to do it ~the hard way~.

Suppose we have the following set of data:

#{5.1, 4.8, 4.2, 4.7, 4.5, 5.2, 4.9, 4.6, 3.9, 4.4, 4.1, 4.0, 4.7, 4.5, 4.2, 4.6, 4.3}#

1) The first step in creating a box-and-whisker plot is ordering your data set:

#{3.9, 4.0, 4.1, 4.2, 4.2, 4.3, 4.4, 4.5, 4.5, 4.6, 4.6, 4.7, 4.7, 4.8, 4.9, 5.1, 5.2}#

2) Second, we need to find the median value: as we have #17# values in the data set, the median will be the #9^(th)# value, that is #4.5#. The median value gives us the second quartile point :

#Q_2 = 4.5#

3) Third, we need to find the other two quartile points , #Q_1# and #Q_3#, by finding the median values of the two data subsets separated by the #Q_2#.

For the first subset #{3.9, 4.0, 4.1, 4.2, 4.2, 4.3, 4.4, 4.5}#, we have 8 values, so its median will be the arithmetic mean of the middle values: #Q_1 = (4.2+4.2)/2 = 4.2#

For the second subset #{4.6, 4.6, 4.7, 4.7, 4.8, 4.9, 5.1, 5.2}#, we also have 8 values, so its median will be the arithmetic mean of the middle values: #Q_3 = (4.7 + 4.8)/2 = 4.75#

4) Fourth, we'll mark the 5 significant values on a scale:

  • the minimum and maximum values: #3.9# and #5.2#
  • the quartiles #Q_1, Q_2 and Q_3#: #4.2, 4.5 and 4.75#

5) Fifth, we draw the box , which goes from #Q_1# to #Q_3#, that is from #4.2# to #4.75#

6) Sixth, we draw the whiskers at the endpoints (minimum and maximum values #3.9# and #5.2#).

In the end, we'll get something like this:
enter image source here

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