Welcome to
Problem Solving
Through
7 QC TOOLS
7 QC Tools
TOOLS
1.
Pareto Diagram
2.
Cause & Effect Diagram
3.
Graphs
4.
Check Sheet / Check List
5.
Scatter Diagram
6.
Histograms
7.
Control Charts
“The term “7 tools for QC” is named after the 7
tools of the famous warrior, Benkei. Benkei owned
7 weapons, which he used to win all his battles.
Similarly, from my own experience, you will find
that you will be able to solve 95% of the problems
around you if you wisely use the 7 tools of QC.”
- ISHIKAWA KAORU, Professor Emeritus,
University of Tokyo
COURSE OBJECTIVE
• Impart a practical understanding in
using Seven QC Tools
• Enable participants to deploy efficient and
effective problem solving methods in BMM
COURSE CONTENTS
Chapter 1 : Problem Solving Process
Chapter 2 : 7 QC Tools : Check Sheets
Chapter 3 : 7 QC Tools : Pareto Chart
Chapter 4 : 7 QC Tools : Histograms
Chapter 5 : 7 QC Tools : Cause and Effects Diagrams
Chapter 6 : 7 QC Tools : Scatter Diagrams
Chapter 7 : 7 QC Tools : Graphs
Chapter 8 : 7 QC Tools : Control Charts
The details Pareto Diagram
The Pareto Diagram is a bar graph with a cumulative curve
connecting the different points. To draw this diagram, the
problems need to be first categorized according to phenomenon
or causes such as defects and corrections, before data is
collected and arranged in order of the number of defects or the
number of corrections. This order is then expressed with the bar
graph.
Cause and Effect Diagram
The cause and effect analysis which was first developed by Professor
Kaoru Ishikawa of the University of Tokyo in the 1940s, is also known
as the ‘Fishbone Diagram’ or the ‘Ishikawa Diagram’
This tool is a picture of lines and symbols designed to represent the
relationship between the effects as problems and the causes
influencing them.
Graphs
Graphs refer to the results of statistical analysis of data (numbers)
which are shown in diagrammatic form to communicate information.
There are numerous types of graphs :
Bar Graph
Belt Graph
Line Graph
Radar Graph
Pie Graph
Check Sheet
Check Sheets are sheets that are designed in advance to collect the
necessary data easily and systematically, which allow the efficient
checking of all items for inspection and verification.
No.
Symptom
Causes
Countermeasure
When
Who
Status
1
Xx
xx
xx
xx
xx
Xx
2
Xx
Xx
Xx
Xx
Xx
Xx
3
xx
Xx
Xx
Xx
Xx
xx
Scatter Diagrams
The scatter diagram is a diagram where the relationship between two
characteristic values are plotted on a graph paper and analyzed as to
whether a correlation exists between the 2 sets of data.This analysis of
correlation will enable you to take the necessary steps to control and
improve the required process.
Histogram
A histogram is a type of bar graph which displays a range of data that
has been grouped into certain classes. It is a useful tool to study the
dispersion of data and analyze certain quality characteristics of the
product or service to which the data in the histogram refers.
Control Charts
The control chart is a chart to examine whether a process is in a
stable condition, or to ensure that the process in maintained in a stable
condition.
The chart collects in time series the movement of data and indicates
any abnormality and normality in the control limit lines. The objective of
control chart is to control the process through ‘accurate judgment,
investigating the real cause, taking prompt measure by showing the
appropriate indicators.
CHAPTER 1
PROBLEM SOLVING
PROCESS
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WHAT IS A PROBLEM ?
• Difficult matter requiring a solution
• Something hard to understand or accomplish
• Whatever stop us doing things better or more effective
• An opportunity for improvement
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DEFINITION OF “ PROBLEM SOLVING”
• A process to analyze problems, to determine and
eliminate root causes.
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PROBLEM SOLVING MODEL
• Problem Identification
• Causal Identification
• Causal Analysis
• Solution Implementation
• Standardization
• Status Monitoring
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POOR PROBLEM SOLVER
• Don’t believe that they can solve problems
• Are impatient and give up quickly
• Are careless readers and may begin working before they
know what the problem is
• Jump to conclusions and expect to go immediately from
what is given to the answer
• Carelessly organise their work or do not organise at all
• Seldom check their work
• Have only one method of working, usually trying to recall
a formula and quitting if they can’t
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GOOD PROBLEM SOLVER
• Believe they can solve just about any problems if they work at it long
enough
• Work for long time on a problem before they give up
• Read problem carefully, often several times, to be certain of what is
asked
• Break problems into small steps, solve the steps one by one, and
look for relationships as they work
• Organise their work carefully so they can stop at any point and trace
their steps
• Check their steps along the way and check their final answer
• Use mental models or drawings to visualise the problems, and try to
remember simpler problems that are related
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PROBLEM SOLVING APPROACH
• Traditional
• Supernatural
• Scientific
• Intuition
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SCIENTIFIC PROBLEM SOLVING APPROACH
• A disciplined process ( e.g PDCA)
• Extensive data collection
• Utilize suitable statistical tools to perform data analysis
and monitoring ( e.g 7 QC Tools)
• Conclude facts based on analysed results
• Periodically review results
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PDCA APPROACH
PLAN
WHAT
Definition of problem
WHY
Analysis of problem
HOW
Identification of causes
Planning countermeasure
DO
CHECK
ACT
Implementation
Confirming effectiveness
Standardizations
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PDCA Vs QC 7 TOOLS
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CHAPTER 2
CHECKSHEET
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Description
• Structure form for collecting and analyzing data. It can
be used to confirm and record that steps of a process
was done
Purpose
• Check sheets are used to systematically collect data.
The data collected may be used to plotting histograms,
pareto charts, etc.
• Can be used as an inspection checksheet, to ensure
that all related items are checked.
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TWO BASIC TYPE OF CHECKSHEET
• Data collecting checksheet
- Process distribution
- Defective items
- Defect location
- Defect cause
• Confirmation checksheet
- Inspection
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Data Collecting Checksheet – (1)
PROCESS DISTRIBUTION CHECKSHEET
• Used for continuous data e.g weight, length, time,
energy etc.
• Used when individual data are not of major importance.
• Used when need to establish the distribution and
relationship to the specifications.
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SAMPLE CHECKSHEET FOR PROCESS DISTRIBUTION
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PROCESS DISTRIBUTION
CHECKSHEET ANALYSIS
• Distribution resemble bell shape, single-peaked,
symmetrical ?
• Centre of the distribution at nominal value ?
• The spread of the data wider than the specification
limits ?
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CONFIRMATION CHECKSHEET
• Used to confirm that the requirements
are fulfilled.
• Used to enable all necessary items are
checked without omission.
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EXAMPLE OF CONFIRMATION CHECKSHEET
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DISADVANTAGE OF CHECKSHEET
• Cannot reveal any changes overtime.
• Possibility of checks not entered by data
collector.
• Need to analyse several sheets arranged in
chronological order to determine the trend.
• Misinterpreting the data due to different
influencing conditions are present.
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CHAPTER 3
PARETO CHART
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DESCRIPTION
• Pareto chart is a bar graph with a cumulative
curve
• The length of the bars represent frequency of
occurrence or cost.
• The pareto chart visually shows which are the
most significant problems, cause or situations.
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HISTORY
• Vilfredo Pareto, a 19th century economist
observed that 80% of wealth was owned by only
20% of the populations.
• 1950 Dr. J.M.Juran discovered that if quality
problems were arranged in order of frequency of
occurrence, relatively few causes accounted for
the bulk of the problems.
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PARETO CHART APPLICATION
• Identify the major problem or concern for
improvements.
• Can be applied for improvement in all areas.
• Shows whether the actions taken are effective.
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CONSTRUCTION OF PARETO CHART
Step 1
Step 2
Step 3
Step 4
Step 5
Determine the problem to be studied
Identify the data to be used, frequency
cost, etc
Identify the categories
Decide the period for data collection
( If comparing the results or different
Pareto chart, the time period should be
the same)
Collect the data and total the frequency
of occurrences in each category
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Step 6
• Arrange the categories in descending order, calculate the
percentage and cumulative percentage for each category.
Example : Cause of Machine Breakdown
Frequency Occur
Frequency %
Cumulative
%
Component failure
20
(20/47) x 100 = 42.6
42.6
Program Hang
14
29.8
72.4
Elec. Contact
4
8.5
80.9
Elec. Component
3
6.4
87.3
Jammed
3
6.4
93.7
Operation
2
4.2
97.9
Others
1
2.1
100
47
100
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Step 7
• On a piece of graph, draw the vertical axis and horizontal
axis.
15
10
5
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Step 8
• Place the categories in the horizontal axis in the
descending order, the category having maximum count on
the left and so on. ( keep all the horizontal scale same
width for all categories )
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Cause of Machine Breakdown
20
A - Component failure
B - Program Hang
15
C - Elec. Contact
D - Elec. Component
10
E - Jammed
5
F - Operation
G - Others
A
B
C
D
E
F
G
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Step 9
Draw the right vertical scale for cumulative percentage, set
the maximum value (100%) on the scale corresponding to
the left vertical axis.
Plot the cumulative percentage line on the chart
Step 10
Give title to all the axis and chart
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Cause of Machine Breakdown
100
F
R
E
Q
U
E
N
C
Y
50
20
C
U
M
.
P
E
R
C
E
N
T
A
G
E
%
A - Component failure
B - Program Hang
15
C - Elec. Contact
D - Elec. Component
10
E - Jammed
5
F - Operation
G - Others
A
B
C
D
E
F
G
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SPECIAL NOTES :
 Choose the categories carefully, ensure that the
categories represent the problem under study.
Eg : To study the high defective rate problem, the categories should
be the type of defect.
 Make sure the terms used are consistent
between data collected and the Pareto chart
 The vertical may represent the followings : Number of defects, reworks or complaint from customer
 Cost
 Time lost or waiting
 Cases of accident
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SPECIAL NOTES (CONT.) :
 The horizontal axis may represent the followings : Type of defects
 Cause of defects
 Different materials
 Different locations, people, machine
 The trick : “ study the data before start plotting the
pareto chart “
 Use Pareto chart to compare before and after
improvement, make sure the data collection
processes are the same.
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EXERCISE 3a
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CHAPTER 4
HISTOGRAM
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Description
• Histogram is a bar graph that shows the distribution of
a set of data
• The shape of the histogram will tell the consistency of
one product or process behavior
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Application
• To show the variability of a process, product, material,
vendor, etc
• To show the central tendency ( mode and mean ) of a
set of measurements.
• To illustrate whether product specifications are met.
• To understand the characteristics of the populations
from which the sample are taken.
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CHARACTERISTICS
• Data are displayed as a series of rectangles of equal
width and varying heights.
• Width represents and interval within the range of data.
• Height represents the number of data values within a
given interval.
• Pattern of varying heights shows the distributions of
data values.
• Pattern provide information on the process behavior.
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SAMPLE OF HISTOGRAM
Frequency
60
50
40
30
20
10
Class
0
1st
Qtr
Interval
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EXERCISE
Data 1 : 3, 4, 4, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 8, 8, 9
Mean =
Range =
Std Dev =
Data 2 : 3, 5.5, 5.6, 5.7, 5.7, 5.7, 6, 6,6, 6,6.3, 6.3,6.3,6.4, 6.5, 9
Mean =
Range =
Std Dev =
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CHAPTER 5
CAUSE AND EFFECT
DIAGRAMS
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DESCRIPTION
• Tool in allowing a team to identify, explore and
graphically display, in increasing details, all of the possible
causes related to a problem or condition to discover its
root cause(s)
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HISTORY
• Developed by Dr. Kaoru Ishikawa in 1943
• Also known as fishbone diagrams or Ishikawa diagrams
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APPLICATION
• Enables a team to focus on the content of the problem,
not on the history of the problem or differing personal
interests of team members.
• Creates a snapshots of the collective knowledge and
consensus of a team around a problem. This builds
support for the resulting solutions.
• Focuses the team on causes, not symptoms.
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TYPES
• Dispersion Analysis
• Process Classification
• Cause Enumeration
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TYPE 1 – DISPERSION ANALYSIS
This is a three step process
Step 1
Write down the effect to be investigated and draw the “backbone” arrow
to it. In the example shown below the effect is “Incorrect deliveries”
“ Causes”
“ Effect”
Incorrect
deliveries
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Step 2
Identify all the board areas of enquiry in which the
causes of the effect being investigated may lie. For
incorrect deliveries the diagram may then become:
Communication
Skills
Incorrect
deliveries
Transport
Procedures
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Step 3
This step requires the greatest amount of work and
imagination because it requires you ( or you and your
team) to write in all the detailed possible causes in each
of the board areas of enquiry. Each cause identified
should be fully explored for further more specific cause
which, in turn, contribute to them.
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Communication
Skills
Lack of information
Picking Slips
procedure
documentation
product
Telephone
Legibility
Knowledge
Order
Picking Slips
ambiguity
literacy
Lack of knowledge
Incorrect
Incorrect dept
deliveries
Incorrect person
consistency
carriers
Customer
Incorrect
database
Address
Not up-to-date
In correct program
Transport
efficiency
manual
automated
methods
correctness
reliability
Procedures
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TYPE 2 – PROCESS CLASSIFICATION
Machine
down during
test
Marketing
Plate
Weighing
Loose Units
In box
Drop units
Lot
Labeling
Materials
Labeling
Testing and
Marketing
Visual
Inspection
Merge Lots
Packing
Mixing
Product
Picking up loose units
Waiting conformation units
Stage too close
Change shift
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TYPE 3 – CAUSE ENUMERATION
• All the possible causes are simply listed ( Brainstorming
session )
• Once all the causes are listed, they are placed in the
major categories in the cause and effect diagrams
• The advantage of this type of diagram is that all identified
causes are listed
• The disadvantage is that it is sometime difficult to relate
all the causes listed to the categories
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BRAINSTORMING
DESCRIPTION
• A technique for tapping creative thinking during the
construction of cause and effect diagram
• Maximize the brainpower of a team
• Use to generate ideas/issues
• Use to clarify ideas/issues
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KEY STEPS IN BRAINSTORMING SESSION
• Identify a facilitator
• Clarify purpose of the session
• Review rules of brainstorming
• Generate ideas taking turns
• Display ideas
• Review ideas for clarification
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ROLES OF FACILITATOR
• Guide brainstorming session
• Ask questions to excite thinking
• Align when session goes off target
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TWO PHASES
• Generation
- Only ideas are generated and no clarification or
analysis carried out
• Clarification
- Ideas generated are clarified if necessary for all to
understand and followed by evaluation of the ideas
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PHASES 1 – IDEAS GENERATION
• Let all members speak freely
• Keep to the rule
• See problem from different angle
• Note all viewpoints
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BRAINSTORMING RULES
• No criticism
• The more ideas, the better
• The wilder the ideas, the better
• Hitch-hike on other ideas; if possible
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PRECAUTIONS OF
BRAINSTORMING
• A strong but not dominating facilitator
• Keep each session to no more than 2 to 3
hour; preferably
• Take relieve breaks after major sections
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NOTE FOR CAUSE AND EFFECT
• Do not confuse cause, effect and
countermeasure
• Use the wisdom and knowledge of the team
• Should not be only problem related, use it for
improvement
• Use as a visual control
• Be innovative when using Cause and effect
diagrams
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READING THE CAUSE AND EFFECT DIAGRAMS
• Pursue the causes actively
- the most probable may not be the most obvious
• Ascertain cause before checking
countermeasure
• Understand the casual relationship to enable
work progress
• Badly arrange cause and effect diagram will
reduce effectiveness
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USING A CAUSE AND EFFECT DIAGRAMS
• Make use of team knowledge through
brainstorming sessions
• Successful countermeasure to be mad into
standards
• Train all to use diagrams
• Continuously use Cause and effect diagram
for each new problem or opportunity
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CAUSE AND EFFECT DIAGRAMS :
GUIDELINES
C5;23.DOC
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