A Box and Whisker What

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A Box and Whisker What???
A detailed guide to making and interpreting Box
and Whisker Plots. Mrs. C. Fisher Whetstone
Elementary
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Box and Whisker Plots
Box and Whisker Plots are a method used to
analyze a given set of data. Lets use some
pretend math scores as a sample data set
77,81, 83, 85, 85, 86, 86, 87, 89, 90, 93, 93,
97, 100
Step 1 Find the Median
We must first identify the median of the data
set. Remember that the median is the middle
number when the data set is ordered from least to
greatest. If there is an even number of numbers
in the data set, then we must find the mean of
the two middle numbers.
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There are 14 numbers so there is no true middle
number!
77,81, 83, 85, 85, 86, 86, 87, 89, 90, 93, 93,
97, 100
 
86 and 87 are the two middle numbers. What is
their mean. 86 87 173 173 divided by 2 is
86.5..The Median
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Not those whiskers, silly!!
Lower Extreme
Upper Extreme
77,81, 83, 85, 85, 86, 86, 87, 89, 90, 93, 93,
97, 100
Step 1 Find the Median
Step 2 Find the Upper and Lower Extreme
This step is easy. The Upper and Lower Extremes
are simply the smallest and largest numbers in
the data set. In our example 77 and 100
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Upper Quartile 93
Lower Quartile 85
Median 86.5
77,81, 83, 85, 85, 86, 86, 87, 89, 90, 93, 93,
97, 100
Upper Extreme
Lower Extreme
Step 1 Find the Median
Step 2 Find the Upper and Lower Extreme
Step 3 Find the Upper and Lower Quartile
The Upper Quartile is simply the median of the
upper half of the data set. The Lower Quartile
is the median of the lower half of the data set.
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Put It All Together
Lower Extreme 77 Lower Quartile 85 Median
86.5 Upper Quartile 93 Upper Extreme 100
Create a number line that spans the set of data
for our example 70-100
Place a vertical line above the Quartiles and
Median. Place a point above the
Extremes. Connect the vertical lines with
horizontal lines to make a rectangle/box. Draw a
line from the box to the Extremes
?
?
70
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85
80
90
100
95
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Youre Done!!

• Analysis When analyzing Box and Whisker Plots,
  it is common to discussing Quartiles (fourths) or
  percents.
• 50 of students did better than 86.5
• The top 25 of students scored about 93 or higher

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