li seven quality tools new

8/4/2019 LI Seven Quality Tools New

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Ishikawa Seven Basic Tools

Sreenivas

[email protected]

Seven Quality Tools

The Seven Tools Histograms, Pareto Charts, Cause and

Effect Diagrams, Run Charts, Scatter

Diagrams, Flow Charts, Control Charts


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Ishikawas Basic Tools of Quality Kaoru Ishikawa developed seven basic visual

tools of quality so that the average person

could analyze and interpret data.

These tools have been used worldwide by

companies, managers of all levels and

employees.

HistogramsSlide 1 of 3

Histogram Defined

A histogram is a bar graph that shows

frequency data.

Histograms provide the easiest way to

evaluate the distribution of data.


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Histograms

Slide 2 of 3 Creating a Histogram Collect data and sort it into categories.

Then label the data as the independent set or thedependent set.

The characteristic you grouped the data by would be theindependent variable.

The frequency of that set would be the dependentvariable.

Each mark on either axis should be in equalincrements.

For each category, find the related frequency andmake the horizontal marks to show that frequency.

HistogramsSlide 3 of 3

Examples of How Histograms Can Be

Used

Histograms can be used to determine

distribution of sales.

Say for instance a company wanted to

measure the revenues of other companiesand wanted to compare numbers.


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When to Use a Histogram

When the data are numerical. When you want to see the shape of the datas distribution,

especially when determining whether the output of a processis distributed approximately normally.

When analyzing whether a process can meet the customers

requirements.

When analyzing what the output from a suppliers processlooks like.

When seeing whether a process change has occurred from onetime period to another.

When determining whether the outputs of two or more

processes are different.

When you wish to communicate the distribution of data quicklyand easily to others.

Summary

The histogram is a graphic representation of

frequency counts of a sample or a population.

The X-axis lists the unit intervals of a parameter

(e.g., severity level of software defects) ranked

in ascending order from left to right, and the Y-

axis contains the frequency counts

The purpose of the histogram is to show the

distribution characteristics of a parameter

It enhances understanding of the parameter of

interest.


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Check List (Sheet)Also called: defect concentration diagram

Definition:

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.

Check sheets help organize data by category.

Check sheets show how many times each

particular value occurs, and theirinformation is increasingly helpful as more

data are collected.

More than 50 observations should be available to becharted for this tool to be really useful.

Check sheets minimize clerical work since the

operator merely adds a mark to the tally on theprepared sheet rather than writing out a figure (Figure

in next slide).

By showing the frequency of a particular defect (e.g.,in a molded part) and how often it occurs in a specific

location, check sheets help operators spot problems.

The check sheet example shows a list of molded partdefects on a production line covering a week's time.

One can easily see where to set priorities based onresults shown on this check sheet.

Assuming the production flow is the same on each day,

the part with the largest number of defects carries thehighest priority for correction.


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Because it clearly organizes data, a check sheet is the easiest

way to track information.

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.


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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 orsimilar 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 sureit 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.


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Phases of Software Development Process in a

company

The software development process consists of multiple phases:

1. Requirements (RQ),

2. System architecture (SD),

3. High-level design (HLD),

4. Low-level design (LLD),

5. Code development (CODE),

6. Unit tests (UT),

7. Integration and building (I/B),

8. Component tests (CT),

9. System tests (ST), and

10. early customer programs (EP).

Each phase has a set of tasks to complete and the phases withformal hand-off have entry and exit criteria.

Check list in Software Process

Checklists help developers and programmers ensure that all

tasks are complete and that the important factors orquality characteristics of each task are covered

Examples of checklists are

design review checklist,

code inspection checklist,

moderator (for design review and code inspection)

checklist,

pre-code-integration (into the system library) checklist, entrance and exit criteria for system tests, and

product readiness checklist.

Checklists are often a part of the process documents.


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Create a Check Sheet

Track up to 10 defects on each day of

the week.

Summary

A check sheet is a paper form with printed items to

be checked.

Its main purposes is to facilitate gathering data and

to arrange data while collecting it so the data can

be easily used later.


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Pareto chartAlso called: Pareto diagram, Pareto analysis

Definition:

A Pareto chart is a bar graph. The lengths of

the bars represent frequency or cost (time or

money), and are arranged with longest bars on

the left and the shortest to the right. In this

way the chart visually depicts which

situations are more significant.

The Pareto diagram is named after Vilfredo Pareto, a 19th-century Italian economist who postulated that a large share of

wealth is owned by a small percentage of the population.

This basic principle translates well into quality problemsmost

quality problems result from a small number of causes.

Quality experts often refer to the principle as the 80-20 rule; thatis, 80% of problems are caused by 20% of the potential sources.

A Pareto diagram puts data in a hierarchical order (Figure in next

slide), which allows the most significant problems to be correctedfirst.

The Pareto analysis technique is used primarily to identify and

evaluate nonconformities, although it can summarize all types ofdata.

It is perhaps the diagram most often used in managementpresentations.

To create a Pareto diagram, the operator collects random data,

regroups the categories in order of frequency, and creates a bar

graph based on the results.


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By rearranging random data, a Pareto diagram identifies and ranks

nonconformities in the quality process in descending order.

Pareto ChartsSlide 1 of 4

Pareto Chart Defined

Pareto charts are used to identify and prioritize

problems to be solved.

They are actually histograms aided by the 80/20

rule adapted by Joseph Juran.

Remember the 80/20 rule states that approximately

80% of the problems are created by approximately 20%of the causes.


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Constructing a Pareto Chart

First, information must be selected basedon types or classifications of defects thatoccur as a result of a process.

The data must be collected and classifiedinto categories.

Then a histogram or frequency chart is

constructed showing the number ofoccurrences.

When to use a Pareto ChartSlide 3 of 4

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 attheir specific components.

When communicating with others about your

data.


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Pareto Chart ExamplesExample #1 shows how many customer complaints were received in

each of five categories.

If all complaints cause equal distress to the customer, working on

eliminating document-related complaints would have the most impact,

and of those, working on quality certificates should be most fruitful.


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Example #2 takes the largest category, documents, from Example #1,

breaks it down into six categories of document-related complaints, and

shows cumulative values.

Pareto Chart in Software Process Pareto analysis helps by identifying areas that cause

most of the problems

Pareto analysis of software defects by category for

four Hewlett-Packard software projects.

The top three types

new function or different processing required,

existing data need to be organized/ presented differently,

and

user needs additional data fields) account for more than

one-third of the defects.

By focusing on these prevalent defect types, determining

probable causes, and instituting process improvements,Hewlett-Packard was able to achieve significant quality

improvements.


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Figure shows an example of a Pareto analysis of the causes

of defects for a product

Summary A Pareto diagram is a frequency chart of bars in

descending order

In software development, the X-axis for a Pareto diagram

is usually the defect cause and the Y-axis the defect

count

By arranging the causes based on defect frequency, a

Pareto diagram can identify the few causes that account

for the majority of defects

It indicates which problems should be solved first in

eliminating defects and improving the operation. Pareto analysis is commonly referred to as the 8020

principle (20% of the causes account for 80% of the

defects), although the cause-defect relationship is not

always in an 8020 distribution.


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Scatter DiagramAlso called: scatter plot, XY graph

Definition:

The scatter diagram graphs pairs of

numerical data, with one variable oneach axis, to look for a relationship

between them. If the variables arecorrelated, the points will fall along a

line or curve.

The better the correlation, the tighterthe points will hug the line.

A scatter diagram shows how two variables arerelated and is thus used to test for cause and

effect relationships.

It cannot prove that one variable causes the

change in the other, only that a relationship

exists and how strong it is.

In a scatter diagram, the horizontal (x) axis

represents the measurement values of one

variable, and the vertical (y) axis represents the

measurements of the second variable.

Figure in next slide shows part clearance values

on the x-axis and the corresponding quantitative

measurement values on the y-axis.


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The plotted data points in a scatter diagram show the relationship

between two variables.

Scatter Diagrams

Scatter Diagrams Defined

Scatter Diagrams are used to study and

identify the possible relationship between

the changes observed in two different sets

of variables.


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Scatter Diagrams

Constructing a Scatter Diagram

First, collect two pieces of data and create asummary table of the data.

Draw a diagram labeling the horizontal andvertical axes.

It is common that the cause variable be labeled on the Xaxis and the effect variable be labeled on the Y axis.

Plot the data pairs on the diagram.

Interpret the scatter diagram for direction and

strength.

Scatter Diagrams

An Example of When a Scatter Diagram

Can Be Used

A scatter diagram can be used to identify

the relationship between the production

speed of an operation and the number of

defective parts made.


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When to Use a Scatter Diagram

When you have paired numerical data.

When your dependent variable may have multiple values foreach value of your independent variable.

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 particularcause and effect are related.

When determining whether two effects that appear to be

related both occur with the same cause.

When testing for autocorrelation before constructing acontrol chart.

Scatter Diagram in Software

Compared to other tools, the scatter diagram is

more difficult to apply. It usually relates to

investigative work and requires precise data

Scatter diagram usually illustrates the relationship

between complexity index and defect level

Each data point represents a program module with

the X coordinate being its complexity index and the

Y coordinate its defect level

Program complexity can be measured as soon as the

program is complete, whereas defects arediscovered over a long time, the positive correlation

between the two allows us to use program

complexity to predict defect level.


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We can reduce the program complexity when it isdeveloped (as measured by McCabe's index),

thereby reducing the chance for defects.

Reducing complexity can also make programs easier

to maintain.

Program modules with high-complexity indexes are

the targets for analysis and possible module

breakup, encapsulation, intramodule cleanup, and

other actions.

Low-complexity indexes coupled with high defects

are clear indications of modules that are poorlydesigned or implemented and should also be

scrutinized.

Scatter Diagram of Program Complexity and Defect Level


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Summary

A scatter diagram vividly portrays therelationship of two interval variables.

Scatter diagrams aid data-baseddecision making (e.g., if action is

planned on the X variable and some

effect is expected on the Y variable).

Cause and Effect DiagramsSlide 1 of 4

Cause and Effect Diagram Defined The cause and effect diagram is also called the Ishikawa diagram

or the fishbone diagram.

It is a tool for discovering all the possible causes for a particular

effect.

The major purpose of this diagram is to act as a first step in

problem solving by creating a list of possible causes.


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Constructing a Cause and Effect Diagram First, clearly identify and define the problem or effect for which

the causes must be identified. Place the problem or effect at theright or the head of the diagram.

Identify all the broad areas of the problem.

Write in all the detailed possible causes in each of the broad areas.

Each cause identified should be looked upon for further morespecific causes.

View the diagram and evaluate the main causes.

Set goals and take action on the main causes.


An Example of When a Cause and Effect DiagramCan Be Used

This diagram can be used to detect the problem ofincorrect deliveries.

Diagram on next slide

Diagram obtained from:

When a production team is about to launch a newproduct, the factors that will affect the final productmust be recognized. The fishbone diagram can depictproblems before they have a chance to begin.


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Diagram of the Incorrect Deliveries Example:

When to Use a Fishbone DiagramAlso Called: Cause-and-Effect Diagram, Ishikawa Diagram

When identifying possible causes for a

problem.

Especially when a teams thinking tends to

fall into ruts.


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Flow ChartsSlide 1 of 3

Flow Charts Defined

A flow chart is a pictorial representation

showing all of the steps of a process.


Creating a Flow Chart

First, familiarize the participants with the flow chart

symbols.

Draw the process flow chart and fill it out in detail

about each element.

Analyze the flow chart. Determine which steps add

value and which dont in the process of simplifying thework.


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Examples of When to Use a Flow Chart

Two separate stages of a process flow chart

should be considered:

The making of the product

The finished product

Run ChartsSlide 1 of 3

Run Charts Defined

Run charts are used to analyze processes

according to time or order.


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Creating a Run Chart Gathering Data

Some type of process or operation must be available to take measurementsfor analysis.

Organizing Data Data must be divided into two sets of values X and Y. X values represent

time and values of Y represent the measurements taken from themanufacturing process or operation.

Charting Data

Plot the Y values versus the X values.

Interpreting Data

Interpret the data and draw any conclusions that will be beneficial to theprocess or operation.


An Example of Using a Run Chart

An organizations desire is to have their product arrive

to their customers on time, but they have noticed that it

doesnt take the same amount of time each day of the

week. They decided to monitor the amount of time it

takes to deliver their product over the next few weeks.


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Control ChartsSlide 1 of 3

Control Charts Defined

Control charts are used to determine whether a

process will produce a product or service with

consistent measurable properties.


Steps Used in Developing Process Control Charts

Identify critical operations in the process whereinspection might be needed.

Identify critical product characteristics.

Determine whether the critical product characteristic isa variable or an attribute.

Select the appropriate process control chart.

Establish the control limits and use the chart to monitorand improve.

Update the limits.


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An Example of When to Use a Control

Chart

Counting the number of defective products or

services

Do you count the number of defects in a given

product or service?

Is the number of units checked or tested constant?

When to Use a Control Chart

When controlling ongoing processes by finding and correcting

problems as they occur.

When predicting the expected range of outcomes from a

process.

When determining whether a process is stable (in statistical

control).

When analyzing patterns of process variation from special

causes (non-routine events) or common causes (built into the

process).

When determining whether your quality improvement project

should aim to prevent specific problems or to make fundamental

changes to the process.


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Activity Process Flow Chart for Finding the Best Way

Home

Construct a process flow chart by making the bestdecisions in finding the best route home.

Refer to the prior notes on flowcharts.

Remember: Define and analyze the process, build a step-bystep picture of the process, and define areas of improvement inthe process.

Answer is on the next slide

Example obtained from:


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SummaryThis presentation provided learning material for each of Ishikawasseven basic tools of quality.

Each tool was clearly defined with definitions, a step-by-step processand an example of how the tool can be used.

As seen through the presentation, these tools are rather simple andeffective.

Works - Cited

Histograms and Bar Graphs.

Your MBA: The Business Study Reference Site.http://yourmba.co.uk/pareto_diagram.htm

Hci Home Services. Cause and Effect Diagram.http://hci.com.au/hcisite/toolkit/causeand.htm

Scatter Diagram. http://sytsma.com/tqmtools/Scat.html

Flowchart.

Run Charts/Time Plot/ Trend Chart.

Foster Thomas S. Managing Quality An Integrative Approach. New Jersey:Prentice Hall, 2001

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