20-12-2012, 03:22 PM
Seven QC Tools
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Check Sheet
Also called: defect concentration diagram
Description
A check sheet is a structured, prepared form for collecting and
analyzing data. This is a generic tool that can be adapted for a wide
variety of purposes.
When to Use a Check Sheet
• When data can be observed and collected repeatedly by the
same person or at the same location.
• When collecting data on the frequency or patterns of events,
problems, defects, defect location, defect causes, etc.
• When collecting data from a production process.
Check Sheet Procedure
• Decide what event or problem will be observed. Develop
operational definitions.
• Decide when data will be collected and for how long.
• Design the form. Set it up so that data can be recorded simply
by making check marks or Xs or similar symbols and so that
data do not have to be recopied for analysis.
• Label all spaces on the form.
• Test the check sheet for a short trial period to be sure it collects
the appropriate data and is easy to use.
• Each time the targeted event or problem occurs, record data on
the check sheet.
Check Sheet Example
The figure below shows a check sheet used to collect data on
telephone interruptions. The tick marks were added as data was
collected over several weeks.
Description
The fishbone diagram identifies many possible causes for an effect or
problem. It can be used to structure a brainstorming session. It
immediately sorts ideas into useful categories.
When to Use a Fishbone Diagram
• When identifying possible causes for a problem.
• Especially when a team’s thinking tends to fall into ruts.
Fishbone Diagram Procedure
Materials needed: flipchart or whiteboard, marking pens
• Agree on a problem statement (effect). Write it at the center
right of the flipchart or whiteboard. Draw a box around it and
draw a horizontal arrow running to it.
• Brainstorm the major categories of causes of the problem. If this
is difficult use generic headings:
o Methods
o Machines (equipment)
o People (manpower)
o Materials
o Measurement
o Environment
• Write the categories of causes as branches from the main arrow.
• Brainstorm all the possible causes of the problem. Ask: “Why
does this happen?” As each idea is given, the facilitator writes it
as a branch from the appropriate category. Causes can be
written in several places if they relate to several categories.
• Again ask “why does this happen?” about each cause. Write subcauses
branching off the causes. Continue to ask “Why?” and
generate deeper levels of causes. Layers of branches indicate
causal relationships.
• When the group runs out of ideas, focus attention to places on
the chart where ideas are few.