7 OLD(BASIC) TOOLS OF QUALITY

HISTORY In 1950, the Japanese Union of

Scientists and Engineers (JUSE) invited W. Edwards Deming to Japan and train Japanese engineers, managers and scholars in statistical process control.

7 OLD(BASIC) TOOLS OF QUALITY

One of the members of the JUSE was Kaoru Ishikawa, the then associate professor at the University of Tokyo. Ishikawa had a desire to 'democratise quality‘

Inspired by Deming’s lectures, he formalized the Seven Basic Tools of Quality Control

7 OLD(BASIC) TOOLS OF QUALITY What are these 7 basic tools??

1.Histograms2.Check sheets 3.Cause and Effect Diagrams4.Pareto Diagrams5.Stratification analysis6.Scatter diagrams &7.Control Charts

HISTOGRAM

Tool for summarizing, analyzing, and displaying data.

To show the different frequencies in a process.

Identify trends and relationships. Graphical representation of the

amount of variation found in a set of data.

HISTOGRAM

CONSTRUCTING HISTOGRAM:1.Data collection2.Calculate the range of the sample data3.Select class scale4.Calculate the size of the class interval.

HISTOGRAM

CONSTRUCTING HISTOGRAM:4. Determine the class boundary5. Calculate the number of data points

(frequency) that are in each class.6. Draw the Histogram

HISTOGRAM

33

65

812

0 0 10

10

20

30

40

50

60

70

1 2 3 4 5 6 7

HISTOGRAM

LIMITATION1.Histograms do not give solutions to

problems. They only provide a starting point for the improvement process.

2.Results obtained from any histogram will depend on the date which the histogram is made.

CHECKSHEET

To collect data from a process in an easy, systematic, and organized manner.

Steps to be taken before data collection.

I. Purpose of collecting dataII.Type of data to be collectedIII.Who is going to collect data and when

CHECKSHEET

TYPES OF CHECKSHEET:

1.Defective Item Check Sheet2.Defective Location Check Sheet3.Defective Cause Check Sheet4.Checkup Confirmation Check Sheet

Data collected using check sheets can be used as input data for other quality tools such as Pareto diagrams

CAUSE AND EFFECT DIAGRAM

Tool that enables the user to set down systematically a graphical representation of the trail that leads ultimately to the root cause of a quality concern or problem.

Also known as fishbone diagram that relates the symptom or problem under question to the factors or causes driving it.

CAUSE AND EFFECT DIAGRAM

Consists primarily of two sides. 1. Right side/effect side, lists the

problem or the quality concern under question. can also include a desired effect the user wishes to achieve

2. Left side/cause side, lists the primary causes of the problem.

CAUSE AND EFFECT DIAGRAM

CAUSE AND EFFECT DIAGRAM

CONSTRUCTING CAUSE AND EFFECT DIAGRAM

Select the team members. Identify quality concern Brain-storming Identify, for each main cause, its related

sub-causes that might effect our quality concern or problem

Focus on one or two causes for which an improvement action(s) can be developed

CAUSE AND EFFECT DIAGRAM

Importance of cause and effect diagram: The structured nature of the method

forces the user to consider all the likely causes of a problem, not just the obvious ones, by combining brainstorming techniques with graphical analysis.

Also useful in unraveling the convoluted relationships that may drive the problem.

PARETO CHART (OR) PARETO ANALYSIS

A Pareto chart is a bar graph. The height of the bars represent frequency or cost (time or money), and are arranged with highest bars on the left and the shortest to the right.

The Pareto 80 / 20 rule80 % of the problems are produced by 20

% of the causes. To identify the ‘VITAL FEW FROM

TRIVIAL MANY’ and to concentrate on the vital few for improvement

A Pareto diagram indicates which problem we should solve first in eliminating defects and improving the operation.

WHEN TO USE When analyzing data about the frequency of problems or causes in a process. When there are many problems or causes and you want to focus on the most significant. When analyzing broad causes by looking at their specific components. When communicating with others about your data.

SCATTER DIAGRAM (OR) SCATTER PLOT

The scatter diagram graphs pairs of numerical data, with one variable on each axis, to look for a relationship between them.

If the variables are correlated, the points will fall along a line or curve. The better the correlation, the tighter the points will hug the line.

When you have paired numerical data. When trying to determine whether the

two variables are related, such as when trying to identify potential root causes of problems.

After brainstorming causes and effects using a fishbone diagram, to determine objectively whether a cause and effect are related.

WHEN TO USE

STRATIFICATION

Stratification is a technique used in combination with other data analysis tools.

When data from a variety of sources or categories have been lumped together, the meaning of the data can be impossible to see

When to Use

Before collecting data. When data come from several sources or

conditions, such as shifts, days of the week, suppliers or population groups.

When data analysis may require separating different sources or conditions.

Process Control Charts

Control charts are tools used to determine whether a process is in a state of control.

Used when the quality of the product depends on some measurable quantity like height, length, diameter etc.

Control Chart

11 22 33 44 55 66 77 88 99 1010Sample numberSample number

UpperUppercontrolcontrol

limitlimit

ProcessProcessaverageaverage

LowerLowercontrolcontrol

limitlimit

Out of controlOut of control

Conditions for Process Control There should be no sample points

outside the upper and lower control limits

Most points should be near the average process line

Points appear randomly distributed

Types of Control Charts

Attributes p-chart c-chart

Variables range (R-chart) mean (x bar – chart)

Control Charts for Attributes p-charts

uses portion defective in a sample c-charts

uses number of defects in an item

p-Chart

UCL = p + zp

LCL = p - zp

z = number of standard deviations from process averagep = sample proportion defective; an estimate of process averagep = standard deviation of sample prop

pp = p = p(1 - (1 - pp)/n)/n

c-Chart

UCL = UCL = cc + + zzcc

LCL = LCL = cc - - zzcc

cc = = c c

where c = number of defects per sample

List Of Seven New Tools of Quality Control Affinity Diagram Relationship Diagram Tree Diagram Matrix Diagram Arrow Diagram Process Decision Program Charts Matrix Data Analysis

History of Seven New Tools Committee set up by Union of Japanese

Scientists and Engineers. - 1972 Aim was to develop more QC techniques with

design approach Work in conjunction with original Basic Seven

Tools Developed to organize verbal data

diagrammatically. Basic 7 tools effective for data analysis,

process control, and quality improvement (numerical data)

Used together increases TQM effectiveness

AFFINITY DIAGRAM

Tool that gathers large amounts of verbal data (ideas, opinions, issues)and organizes them into groups.

Organization based on natural relationships

This makes it feasible for further and analysis and to find a solution to the problem.

Sample Affinity Diagram

Why Affinity Diagrams…

Good way to get people to work on a creative level to address difficult issues.

Can be used in situations unknown or unexplored by a team.

Fosters team spirit. Raises team awareness

How to construct Affinity Diagrams(Group Method Approach) Select a topic Collect verbal data by brainstorming Discuss collected info until everyone

understands it thoroughly Write each item on a separate data card Organize data cards into groups of similar

themes(natural affinity) Combine statements on data cards to new

Affinity statement Make new cards with affinity statement Complete the diagram

RELATIONSHIP DIAGRAM

Also known as inter-relationship diagram

Used to depict the relationship between different issues

Helps to untangle and find logical relations among complex intertwined causes and effects

Allows for multidirectional thinking rather than lateral thinking

Advantages of Relationship Diagram Useful at planning stage for obtaining

perspective on overall situation Facilitates consensus among team Assists to develop and change people’s

thinking Enables priorities to be identified

accurately Makes the problem recognizable by

clarifying the relationships among causes

A Sample Relationship Diagram

How to Construct a relationship Diagram

Express the problem List the causes affecting the problem Write each item on a card Move the cards into similar groups explore the cause-effect relationships, and divide the cards

into primary, secondary and tertiary causes Connect all cards by these relationships Further discuss until all possible causes have been

identified Review whole diagram looking for relationships among

causes Connect all related groups Complete the diagram

TREE DIAGRAM

It starts with one item that branches into two or more, each of which branch into two or more, and so on. It looks like a tree, with trunk and multiple branches.

It is used to break down broad categories into finer and finer levels of detail. Developing the tree diagram helps you move your thinking step by step from generalities to specifics.

When to use a tree diagram When an issue is known or being addressed in

broad generalities and you must move to specific details.

When developing actions to carry out a solution or other plan.

When analyzing processes in detail. When probing for the root cause of a problem. When evaluating implementation issues for

several potential solutions. After an affinity diagram or relations diagram

has uncovered key issues. As a communication tool, to explain details to

others.

Procedure Determine the main goal Be concise Brainstorm the main tasks involved in

solving the problem and add them to the tree

Brainstorm subtask that can also be added to the tree

Do this until all possibilities have been exhausted

To Accomplish

3rd means

3rd means

Primary means

3rd means

3rd means

Primary means

Secondary means

Secondary means

Secondary means

Secondary means

3rd means

3rd means

3rd means

3rd means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

4th means

Example

PROCESS DECISION PROGRAM CHART (PDPC) It is a good tool to use for contingency

planning. It identifies what might go wrong in a

plan under development. We can either revise the plan to avoid

the problems or be ready with the best response when a problem occurs.

Example :

Procedure

List the steps in the process you wish to

analyze

List what could go wrong at each step

List the counter measures to the problems

Evaluate the counter measures by placing

an O for feasible or an X for not feasible

MATRIX DATA ANALYSIS

One of the most rigorous, careful and time-consuming of decision-making tools

It is an L-shaped matrix that uses pair-wise comparisons of a list of options to a set of criteria in order to choose the best option(s).

Based solely on numerical data

Procedure

Identify your goal Place selection in order of importance Apply percentage weight to each option Sum individual ratings to establish overall

ranking Rank order each option with respect to

criterion Multiply weight by associated rank in Matrix Result is Importance Score Add up Importance Scores for each option

Particulars

CustomerD

CustomerM

CustomerR

CustomerT

Purity % > 99.2 > 99.2 > 99.4 > 99.0

Trace metals (ppm)

< 5 — < 10 < 25

Water (ppm)

< 10 < 5 < 10 —

Viscosity (cp)

20-35 20-30 10-50 15-35

Color < 10 < 10 < 15 < 10

Drum      

Truck     

Railcar      

Example – Customer requirements

Matrix Diagram

The matrix diagram shows the relationship between

two, three or four groups of information. It also can

give information about the relationship, such as its

strength, the roles played by various individuals or

measurements

Six differently shaped matrices are possible: L, T, Y,

X, C, R and roof-shaped, depending on how many

groups must be compared.

When do we use each Shape

An L-shaped matrix relates two groups of items to each other (or one group to itself).

A T-shaped matrix relates three groups of items: groups B and C are each related to A. Groups B and C are not related to each other.

A Y-shaped matrix relates three groups of items. Each

group is related to the other two in a circular fashion.

A C-shaped matrix relates three groups of items all together simultaneously, in 3-D.

An X-shaped matrix relates four groups of items. Each group is related to two others in a circular fashion.

A roof-shaped matrix relates one group of items to itself. It is usually used along with an L- or T-shaped matrix. (Used in QFD)

TYPES OF MATRICES

ARROW DIAGRAM (OR) NETWORK DIAGRAM (OR) CPM (CRITICAL

PATH METHOD) CHART

The arrow diagram shows the required order of tasks in a project or process, the best schedule for the entire project, and potential scheduling and resource problems and their solutions.

When scheduling and monitoring tasks

within a complex project or process with interrelated tasks and resources.

When you know the steps of the project or process, their sequence and how long each task.

When project schedule is critical, with serious consequences for completing the project late or significant advantage to completing the project early.

R CHART AND X BAR CHART An X-bar and R (range) chart is a pair of control

charts used with processes that have a subgroup size of two or more.

The standard chart for variables data, X-bar and R charts help determine if a process is stable and predictable.

The X-bar chart shows how the mean or average changes over time and the R chart shows how the range of the subgroups changes over time.

It is also used to monitor the effects of process improvement theories. As the standard, the X-bar and R chart will work in place of the X-bar and s or median and R chart

Used for measurement data Assumes population is normally distributed. Upper and lower control limits usually 3

standard deviations above and below the mean of the process.

Collect small samples in equally spaced intervals over time.z

Usually 20-30 periods n is the sample size collected each time k is the number of samples collected over time

For each sample, calculate the mean A.M x = x/N For each sample, calculate the range range = xlargest – xsmallest Calculate the grand or overall mean by

averaging all the sample means. This becomes the center line of the x-

bar chart.