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| Math
A |
Box-and-Whisker
Plots |
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Data
can be displayed in many ways. One method of displaying a
set of data is with a box-and-whisker plot.
Box-and-whisker plots are helpful in interpreting the
distribution of data. |
We know that the median
of a set of data separates the data into two equal parts.
Data can be further separated into quartiles.
The first
quartile is the median of the
lower part of the data.
The second quartile
is another name for the median of the entire set of data.
The third quartile
is the median of the upper part of the data.
Quartiles separate the
original set of data into four equal parts. Each of these parts
contains one-fourth of the data.
Constructing
a box-and-whisker plot:
The data:
Math test scores 80, 75, 90, 95, 65, 65, 80, 85, 70, 100
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Write the data in numerical
order and find the first quartile, the median, the third
quartile, the smallest value and the largest value.
median =
80
first quartile = 70
third quartile = 90
smallest value = 65
largest value = 100 |
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Place a circle beneath each of these
values on a number line. |
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Draw a box with ends through the points
for the first and third quartiles. Then draw a vertical line through the box at the
median point. Now, draw the whiskers (or lines) from each end of the
box to the smallest and largest values. |
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Special
Case:
You may see a box-and-whisker plot, like the one below,
which contains an asterisk.
Sometimes there is ONE piece of data that falls well outside the range
of the other values. This single piece of data is called an outlier.
If the outlier is included in the whisker, readers may think that there are
grades dispersed throughout the whole range from the first quartile to the
outlier.
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How to use
your
TI-83+ graphing calculator with
box and whisker plots.
Click calculator. |
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