3.3 GRAPHICAL DISPLAYS OF DATA

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3.3 GRAPHICAL DISPLAYS OF DATA

• 3.3.1 Graphical Displays for Qualitative Data
• There are two methods that you can use to display
  qualitative data, a bar chart and a pie chart.
• A bar chart represents the frequency or relative
  frequency from the table in the form of a
  rectangle or bar.

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3.3 GRAPHICAL DISPLAYS OF DATA

• 3.3.1.1 Creating a Bar Chart for Qualitative Data
• In a bar chart, one of the axes is used to
  represent the categories from the frequency table
  and the other axis is used to represent the
  frequency or relative frequency for the
  categories.
• Step 1 Draw a pair of axes, x and y.
• Step 2 At evenly spaced intervals on the x axis
  put tick marks and label them with the categories
  from the frequency table.

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3.3 GRAPHICAL DISPLAYS OF DATA

• Step 3 Scale the y axis so that the category
  with the highest frequency or relative frequency
  can be graphed. Choose the scale so that you can
  distinguish different frequencies or relative
  frequencies from each other.
• Step 4 At each category on the x axis, draw a
  rectangle (bar) whose height is equal to the
  frequency or relative frequency for the category.
  The bases of the rectangles must be the same
  width and the bars should not touch each other.

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3.3 GRAPHICAL DISPLAYS OF DATA

• Step 5 Label the axes and give the graph an
  appropriate title.

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3.3 GRAPHICAL DISPLAYS OF DATA

• 3.3.1.2 Pareto Analysis
• An important application of bar charts in the
  area of management is in Pareto analysis.
• Very often, managers are faced with numerous
  situations and problems that are not of equal
  importance.

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3.3 GRAPHICAL DISPLAYS OF DATA

• This principle, known as the principle of "the
  vital few and the trivial many" or the "80-20
  rule," was named the Pareto principle in the
  1940s by J. M. Juran, one of the major
  contributors in the field of Total Quality
  Management (TQM).
• A Pareto diagram is a bar chart in which the
  categories are plotted in order of decreasing
  relative frequency.

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