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