7 QC Tools

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