About 7 QC Tools
What
do we mean by 'tools'?
In
beginning a column on tools, perhaps the first question that must be asked, is
'What do we mean by tools, particularly in the context of quality?' Quality
tools may be described as, 'Structured activities that contribute towards
increasing or maintaining business quality'. Let's look closer at
this description:
'Structured
activities' means doing things in a repeatable way, using a defined set of
rules,
'that
contribute' means
that they add value.
'increasing
or maintaining' means
that they can be used for all areas of quality improvement, control and
management.
'business
quality' means
that the company benefits from their use.
Tools
may be used at the organisational level, structuring the way people work
together, or at the individual level, helping people and groups to solve
problems and do their jobs.
Three
areas to use tools
Broadly,
individual tools are used to manage information in three areas:
1.
Collecting various levels of numeric and non-numeric information.
2.
Structuring that information in order to understand aspects of processes and
problems.
3.
Using the information to identify and select information and plan for specific
actions.
So what are
the individual tools, and where do they come from? There are several sources:
Seven tools and more...
The
Japanese have collected (and even invented some of) two sets of seven tools,
although just to confuse us, there are conflicting views on what these
are. For example, some descriptions of the first seven tools include
Flowcharts, whilst others include Bar Charts or Line Graphs.
Work
Study, a predecessor of modern quality, has given us tools for measuring our
work, for example the Flow Process Diagram and the String Diagram.
Specialised
quality areas, such as reliability engineering, have give tools such as PFMEA.
There
are a number of general management tools for planning and decision-making, such
as Gantt Charts and Decision Trees.
Computer
programming has given us several tools for mapping out processes, the most
common being Flowcharts.
There
are many other areas that yield useful tools, for example SWOT Analysis from
marketing.
Below
is a Matrix Diagram taken from my forthcoming book, used to relate a number of
individual tools to the three application areas described above.
APPLICATIONS FOR TOOLS
This
reviews the situations where there is a need for tools in quality improvement
and problem solving and identify an eight-stage universal problem-solving project
framework that may be used to manage the overall project.
·
Introduction: Overview of what it's all
about
·
A framework for process improvement: A
generic project framework.
1 Identify
2 Define
3 Problem
4 Cause
5 Solution
6 Implement
7 Review
8 Follow-up
·
Applications in process improvement projects
SEVEN
QC TOOLS
1.
CHECK SHEET
2.
HISTOGRAM
3.
PARETO DIAGRAM
4.
CAUSE AND EFFECT DIAGRAM
5.
SCATTER DIAGRAM
6.
STRATIFICATION
7.
GRAPHS AND CONTROL CHARTS
1. CHECK
SHEET
- THIS IS A
DATA COLLECTION DEVICE ORIENTED TOWARDS DEFECT PREVENTION
- DEFECT
PREVENTION IS THE GOAL OF QUALITY CONTROL
- CONSIDER
THE FOLLOWING CYCLE
> DEFECT PREVENTION
> MEANS PREDICTION
> MEANS FOLLOWING STATISTICAL LAWS OF BEHAVIOUR
> MEANS USE OF DATA
> WHICH COMES FROM INSPECTION
HENCE FOR
A GOOD DEFECT PREVENTION PROGRAM, THE INSPECTION SYSTEM SHOULD BE VERY STRONG
THIS MEANS
GOOD PLANNING FOR DATA COLLECTION
DATA
COLLECTION DEVICE CAN BE IN THE FORM OF:
1. TABULAR STRUCTURE
2. PICTORIAL (LOCATION TYPE)
3. GRAPHICAL
4. MATRIX STRUCTURE
5. CHECK LIST STRUCTURE
2. HISTOGRAM
HISTOGRAM
CAN ALSO BE CONSIDERED AS A CHECK SHEET
- HISTOGRAM
IS A FREQUENCY DIAGRAM
- THIS IS
MORE APPLICABLE FOR MEASUREMENT DATA
- THE X-AXIS
IS THE MEASUREMENT AND THE Y-AXIS IS THE FREQUENCY
- THE
SPACING IN THE X-AXIS IS UNIFORM AND THE FREQUENCY IS REPRESENTED BY A BAR
DIAGRAM
- THE X-AXIS
IS ORDERED IN THE SENSE THAT IT STARTS FROM THE SMALLEST AND ENDS WITH THE
HIGHEST COVERING THE ENTIRE RANGE
- THE HEIGHT
OF THE BAR IN THE Y-AXIS IS PROPORTIONAL TO THE FREQUENCY
- THE BARS
ARE ARRANGED SO THAT THEY TOUCH EACH OTHER HORIZONTALLY
DRAW THE
HISTOGRAM
THERE ARE
FOUR INTERPRETATIONS FOR THE HISTOGRAM:
1. LOOK AT THE SPECIFICATIONS – IT INDICATES THE
ACCEPTANCE AND REJECTION OR NON-CONFORMANCE
2. LOOK AT THE PEAK – IT REPRESENTS THE SETTING
3. LOOK AT THE WIDTH – IT REPRESENTS THE CAPABILITY
4. LOOK AT THE SHAPE – IT REPRESENTS THE PREDICTABILITY
3. PARETO
DIAGRAM
IT IS
NAMED AFTER THE ITALIAN ECONOMIST PARETO
IT
REPRESENTS AN IMPORTANT LAW OF LIFE!
- THIS IS ANOTHER ORDERED BAR DIAGRAM
- THE X-AXIS REPRESENTS CATEGORIES
- THE Y-AXIS REPRESENTS CONTRIBUTION IN PERCENTAGE TERMS
- THE X-AXIS IS SPACED UNIFORMLY
- THE Y-AXIS
IS REPRESENTED BY BARS WHOSE HEIGHT IS EQUIVALENT TO THE PERCENTAGE
CONTRIBUTION TO THE TOTAL
- THERE IS
AN ORDER IN THE ARRANGEMENT OF THE BARS. THE LEFT SIDE STARTS FROM THE HIGHEST
AND GOES DOWN IN THE DESCENDING ORDER TOWARDS THE RIGHT
- A
CUMULATIVE LINE IS ALSO SHOWN IN THE DIAGRAM. THIS CUMULATIVE LINE IS USED TO
IDENTIFY THE VITAL FEW FROM THE USEFUL MANY.
- THIS
PROPERTY OF DISTINGUISHING THE VITAL FEW FROM THE USEFUL MANY IS THE UNDERLYING
PHILOSOPHY OF THE PARETO PRINCIPLE
- THERE IS A
BASIC LAW OF NATURE - THERE ARE ONLY A
FEW ITEMS CONTRIBUTING TO A MAJOR SHARE OF THE OUTPUT. HENCE, BY CONTROLLING
THE FEW CONTRIBUTORS A GREAT BENEFIT CAN BE DERIVED.
- OBVIOUSLY
THERE IS A MANAGEMENT PRINCIPLE HIDDEN IN THIS LAW
DRAW THE
PARETO DIAGRAM
4. CAUSE
AND EFFECT DIAGRAM
THIS IS
ALSO KNOWN AS ISHIKAWA DIAGRAM NAMED AFTER THE PERSON WHO INVENTED IT. OTHER
NAMES ARE FISHBONE DIAGRAM, WINDOWS OF TECHNOLOGY.
- THIS
TECHNIQUE IS BASED ON THE BELIEF THAT THERE IS A CAUSE OR THERE ARE CAUSES,
WHICH AFFECT ANY OUTPUT.
- THIS IS A
STRUCTURED WAY OF CAPTURING ALL THE CAUSES AFFECTING A GIVEN EFFECT
- BRAINSTORMING
IS A GOOD STARTING POINT FOR THIS TECHNIQUE
- THE KEY
SUCCESS FACTOR IN THIS TECHNIQUE IS THE ABILITY TO INVOLVE ALL CONCERNED IN AN
ORGANISATION (INCLUDING WORKMEN)
- THE
TECHNIQUE OFFERS A GOOD CLASSIFICATION OF THE CAUSES FOR FURTHER ACTION
- THE CLASSIFICATION
CAN BE MAN MACHINE, METHOD, ETC. OR IT CAN BE PROCESS STAGE WISE OR IT CAN BE
PART WISE FOR AN ASSEMBLY, ETC.
- THIS
TECHNIQUE CAN BE INNOVATIVELY USED FOR THE FOLLOWING:
1. TRAINING
2. DATA COLLECTION
3. PROBLEM SOLVING DISCUSSIONS
4. ON LINE UPDATION OF KNOWLEDGE
5. FURTHER EXPLOSION OF EACH SUB CAUSE
- THIS
TECHNIQUE IS THE FOUNDATION FROM WHICH OTHER TECHNIQUES FOR THE FOLLOWING ARE
BUILT:
1. ROOT CAUSE ANALYSIS
2. MASTER CAUSE ANALYSIS TECHNIQUE
- THE CAUSE
SHOULD REFLECT ON THE NATURE OF THE PROBLEM. WE SHOULD DIFFERENTIATE BETWEEN
TECHNOLOGICAL CAUSES AND PROBLEM RELATED CAUSES. FOR EXAMPLE: TEMPERATURE MAY
NOT BE A CAUSE. TEMPERATURE WILL BE A REQUIREMENT WHEREAS TEMPERATURE VARIATION
WILL BE A CAUSE
DRAW CAUSE
AND EFFECT DIAGRAM
5. SCATTER DIAGRAM
- THIS IS A DIAGRAM, WHICH DEPICTS RELATIONSHIP AND ITS NATURE. RELATIONSHIP IS ALSO REFERRED AS CORRELATION
- IT IS TO EXAMINE THE RELATIONSHIP BETWEEN TWO VARIABLES & LEVEL OF RELATIONSHIP
Eg. RELATIONSHIP BETWEEN NUMBER OF COMPLAINTS AND NUMBERS OF MACHINES UNDER REPAIRS.
- IT IS A GRAPH WITH THE INDEPENDENT VARIABLE (CAUSE) ON THE
X-AXIS AND THE DEPENDENT VARIABLE (EFFECT) ON THE Y-AXIS
- THIS TECHNIQUE REQUIRES MEASURABLE DATA FOR ITS APPLICATION
- THE SCALE SHOULD BE CHOSEN CORRECTLY FOR THE VISUAL ANALYSIS IN THIS TECHNIQUE
- SOME APPLICATIONS OF THIS TECHNIQUE:
1. FOR KNOWING THE EXISTENCE OF RELATIONSHIP
2. FOR PROVIDING SPECIFICATIONS AND TOLERANCE
3. FOR FURTHER COMPLEX ANALYSIS LIKE REGRESSION AND ESTABLISHING OF NATURE OF RELATIONSHIP AND EXTENT OF RELATIONSHIP
4. FOR QUALITY ENGINEERING
5. SCATTER
DIAGRAM
- THIS IS A
DIAGRAM, WHICH DEPICTS RELATIONSHIP AND ITS NATURE. RELATIONSHIP IS ALSO REFERRED AS CORRELATION
- IT IS TO
EXAMINE THE RELATIONSHIP BETWEEN TWO VARIABLES & LEVEL OF RELATIONSHIP
Eg. RELATIONSHIP BETWEEN NUMBER OF COMPLAINTS AND
NUMBERS OF MACHINES UNDER REPAIRS.
- IT IS A
GRAPH WITH THE INDEPENDENT VARIABLE (CAUSE) ON THE
X-AXIS AND THE DEPENDENT VARIABLE (EFFECT) ON THE Y-AXIS
- THIS
TECHNIQUE REQUIRES MEASURABLE DATA FOR ITS APPLICATION
- THE SCALE
SHOULD BE CHOSEN CORRECTLY FOR THE VISUAL ANALYSIS IN THIS TECHNIQUE
- SOME
APPLICATIONS OF THIS TECHNIQUE:
1. FOR KNOWING THE EXISTENCE OF RELATIONSHIP
2. FOR PROVIDING SPECIFICATIONS AND TOLERANCE
3. FOR FURTHER COMPLEX ANALYSIS LIKE REGRESSION AND
ESTABLISHING OF NATURE OF RELATIONSHIP AND EXTENT OF RELATIONSHIP
4. FOR QUALITY ENGINEERING
6. STRATIFICATION
- THIS
TECHNIQUE HAS TO BE THE FUNDAMENTAL PRINCIPLE BEHIND DATA COLLECTION
- STRATIFICATION
HAS TO BE PLANNED IN ADVANCE OF DATA COLLECTION
- STRATIFICATION
MEANS SUB-LAYERING OR ANALYSING A SITUATION COMPONENT OR INDIVIDUAL CONTRIBUTOR
WISE. EXAMPLE: MACHINE WISE, SHIFT WISE, BATCH WISE, PRODUCT WISE, ETC.
- STRATIFICATION
CAN BE DONE IN THE SHOP ONLY IF WE IDENTIFY THE COMPONENTS IN A PLANNED WAY.
- THERE ARE
TWO TYPE OF STRATIFICATION THAT CAN BE DONE – PAPER IDENTIFICATION OR
PART/PRODUCT IDENTIFICATION
- STRATIFICATION
CAN BE DESIGNED INTO THE BASIC DATA SYSTEM OR IT HAS TO BE DONE WHEN WE FACE A
PROBLEM LIKE CUSTOMER COMPLAINTS OR PRODUCT NON-CONFORMANCE
- STRATIFICATION
CAN BE PLANNED AS A PART OF THE ANALYSIS AFTER THE CAUSE AND EFFECT DIAGRAM
7. GRAPHS AND CONTROL CHARTS
> GRAPHS:
- THESE ARE
VISUAL DEPICTION OF DATA TO FACILITATE EASY UNDERSTANDING AND FOR TAKING
IMMEDIATE ACTION
- THE
SUCCESS OF THIS TECHNIQUE DEPENDS ON THE CORRECT USAGE. TYPICAL CORRECT USAGE
INCLUDES:
1. USING ONLINE
2. PLOTTING THE DATA IN THE ORDER OF OPERATION
3. TAKING TIMELY CORRECTIVE ACTION
4. ABILITY TO DISTINGUISH BETWEEN RANDOM VARIATION AND
SPECIFIC PATTERN
- LINE GRAPH
IS A VERY POPULAR GRAPH
- CRITERIA
FOR SELF CONTROL IS TO BE FULFILLED
- SELF
CONTROL MEANS:
1. KNOWLEDGE OF WHAT IS TO BE DONE
2. KNOWLEDGE OF WHAT IS BEING DONE
3. MEANS TO TAKE REGULATORY ACTION
- TARGET
LINES AND TREND ANALYSIS ARE VERY IMPORTANT FOR ANALYSIS
> CONTROL CHARTS:
- THEY ARE A
TYPE OF GRAPH
- ALL THE
POINTS DISCUSSED FOR GRAPHS ARE APPLICABLE
- DATA ARE
COMPARED TO COMPUTE CONTROL LIMITS, WHICH ARE ALSO CALLED PROCESS LIMITS. THESE
LIMITS ARE COMPUTED BASED ON ACTUAL PAST DATA
- RUNNING A
PROCESS IN A PREDICTABLE FASHION IS THE GOAL OF THE CONTROL CHARTS
- TIMELY
ACTION ON OUT OF CONTROL POINTS IS THE KEY TO THE SUCCESS OF THIS TECHNIQUE
- ANY
CONTROL CHART CONSISTS OF THREE LINES (UPPER CONTROL LIMIT, MEAN, LOWER CONTROL
LIMIT)
- THERE ARE
DIFFERENT TYPES OF CONTROL CHARTS DEPENDING ON THE NATURE OF DATA USED LIKE
VARIABLE AND ATTRIBUTE DATA
- SOME
CONTROL CHARTS ARE X-BAR CHART, p CHART, c CHART.
- A CONTROL
CHART CORRECTLY USED CAN ACHIEVE THE FOLLOWING SIMULTANEOUSLY:
1. REDUCING VARIATION
2. INCREASING PRODUCTIVITY
3. REDUCING COST BY ELIMINATING INSPECTION
