The Magnificent Seven Tools for Process Quality Improvement

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The Magnificent Seven Tools for Process Quality
Improvement

• BUAD 820
• Data Analysis Quality Management

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The Magnificent Seven

• The seven major tools are
• 1) Flowchart or process mapping
• 2) Check Sheet
• 3) Histogram or Stem and Leaf plot
• 4) Pareto Chart
• 5) Cause and Effect Diagram
• 6) Scatter Diagram
• 7) Control Chart

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Flowcharts

• Identifies the sequence of activities or the flow
  of materials and information in a process
• Can be useful in pin-pointing problems,
  error-proofing the process, streamlining it by
  eliminating non-value added steps, and in
  reducing variation

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Example of a process flow chart
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Check Sheets

• Check sheets customized data collection forms
  designed to collect relevant operating data about
  the process under investigation
• A check sheet can range from being very simple,
  to very complex involving different dimensions
  (time of the day, day of the week, source of
  production, raw material used)
• You can read more about check sheets here
  http//www.hci.com.au/hcisite3/toolkit/data.htm

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Check sheet for the process of handling of
returned goods at a company
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Data organizing tools

• Once collected, raw data is typically summarized
  (reduced, or compacted) this can be done in
  several ways
• Stem-and-leaf plot
• Frequency distributions
• Histograms

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Raw data on the bursting strength of 100 randomly
selected soda bottles
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Stem and leaf plot for bursting strength data
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The Frequency Distribution and Histogram

• Frequency Distribution
• Arrangement of data by magnitude
• More compact than a stem-and-leaf display
• Graphs of observed frequencies are called
  histograms.

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Frequency distribution for soda bottle bursting
strength data
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Histogram for soda bottle bursting strength data
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Graphical Displays

• What is the overall shape of the data?
• Are there any unusual observations?
• Where is the center or average of the data
  set located?
• What is the spread of the data? Is the data
  spread out or close to the center?

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Pareto Chart

• The Pareto chart is a frequency distribution (or
  histogram) of attribute data arranged by
  category.
• Plot the frequency of occurrence of each defect
  type against the various defect types.

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Reasons for nonconforming soda bottles
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Pareto chart for reasons of nonconformance
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Cause and Effect Diagram

• Once a defect, error, or problem has been
  identified and isolated for further study,
  potential causes of this undesirable effect must
  be analyzed
• Cause and effect diagram is a useful way of
  categorizing potential causes leading to a
  quality problem
• Read more about cause and effect diagram here
  http//www.hci.com.au/hcisite2/toolkit/causeand.ht
  m

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How to Construct a Cause-and-Effect Diagram

• Define the problem or effect to be analyzed.
• Form the team to perform the analysis. Often the
  team will uncover potential causes through
  brainstorming.
• Draw the effect box and the center line.
• Specify the major potential cause categories and
  join them as boxes connected to the center line
• Identify the possible causes and classify them
  into the categories in step 4. Create new
  categories, if necessary.
• Rank order the causes to identify those that seem
  most likely to impact the problem.
• Take corrective action.

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Cause and effect diagram for incorrect deliveries
made by a package delivery company
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Scatter Diagram

• The scatter diagram is a plot of two variables
  that can be used to identify any potential
  relationship between the variables
• The shape of the scatter diagram often indicates
  what type of relationship may exist

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Scatter plot for relationship between apartment
size and its rent (n25)
Scatter plot suggests that there is a positive,
linear relationship between Rent and Size
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Control Charts

• Types the control chart
• Variables Control Charts
• These charts are applied to data that follow a
  continuous distribution (measurement data)
• Attributes Control Charts
• These charts are applied to data that follow a
  discrete distribution

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Control chart examples

• Attribute chart for percent of non-ready rooms at
  a major hotel

• Variable chart for average delivery time for
  baggage handlers at the same hotel

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Popularity of Control Charts

• 1) Control charts are a proven technique for
  improving productivity.
• 2) Control charts are effective in defect
  prevention.
• 3) Control charts prevent unnecessary process
  adjustment.
• 4) Control charts provide diagnostic information.
• 5) Control charts provide information about
  process capability.