Box and Whisker Plots

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Box and Whisker Plots

• An interactive lesson

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Introduction

• A box-and-whisker plot can be useful for handling
  many data values.
• They allow people to explore data and to draw
  informal conclusions when two or more variables
  are present.
• It shows only certain statistics rather than all
  the data.
• Box and whisker plots consists of the median the
  quartiles and the smallest and greatest values
  in the distribution.

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How to make a Box and Whisker Plot

• Put your set of date in increasing numerical
  order (if it isnt already). Example100
  27 34 54 59 18 52 61 78 68 82 87 85
  93 91. Should now look like this 18 27
  34 52 54 59 61 68 78 82 85 87 91 93
  100.

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Step 2 - Median

• Find the median of your set of dataRemember
  the median is the value exactly in the middle of
  an ordered set of numbers 18 27 34 52 54
  59 61 68 78 82 85 87 91 93 100.
• Q What would you do it you had an even set of
  numbers

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Step 3 Lower Quartile

• Next we consider only the values to the left of
  the median
• 18 27 34 52 54 59 61 68 78 82 85 87
  91 93 100.
• We find the median of those numbers
• 18 27 34 52 54 59 61
• Q This number is call the lower quartile. Can
  you guess why

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Step 4 Upper Quartile

• Next we consider only the values to the right of
  the median
• 18 27 34 52 54 59 61 68 78 82 85 87
  91 93 100.
• We find the median of those numbers
• 78 82 85 87 91 93 100.
• Q This number is call the upper quartile. Can
  you guess why

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Step 5 Highest/Lowest Values

• Now indicate your lowest and highest values
• 18 27 34 52 54 59 61 68 78 82 85 87
  91 93 100.

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Step 6 - Drawing

• Now we are ready to begin to draw our graph.
• 18 27 34 52 54 59 61 68 78 82 85 87
  91 93 100.
• Plot the lowest value lower quartile median
  upper quartile and the highest value on a
  number line.

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• Put a line through the Lower Quartile Median
  and Upper Quartile.
• Then Put a box around those lines

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• Lastly draw a line from your extreme values to
  the box
• There is your Box and Whisker Plot
• Q Can you guess where the graph gets its
  name

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• Time for a challenge activity