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9- 10

Quality ImprovementTools

Quali ty is free, bu t only to th ose wh o are wil l in g to pay heavi ly

for i t .

Philip Crosby

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Learning Objectives

After studying this chapter, you should be able to:

I. Explain the seven Quality control tools

Pareto Chart

Cause and Effect Diagram

Check sheet

Histogram

Scatter Diagram

Control Charts

Graph

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Seven QC Tools

The Seven Q.C. Tools were identified by the Japanese Union

of Scientists and Engineers (JUSE) as the seven most

important tools for use in Continuous Improvement.

They are primarily associated with the Study and Act steps

in the PDSA cycle. The Seven Q.C. Tools are often used in conjunction with a step-by-step

problem solving process known as the Q.C. Story.

The seven QC tools are Pareto Chart, Cause and Effect

Diagram, Stratification, Check sheet, Histogram, ScatterDiagram, Control Charts and graph

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1. Pareto Chart

A Pareto chart is a bar graph. The lengths ofthe 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. Pareto Chart is a special

form of a bar graph and is used to display the

relative importance of problems or conditions.

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Steps in Constructing a Pareto Chart

List the activities or causes in a table and their frequency of occurrence

Place these in descending order of magnitude in the table

Calculate the total for the whole list

Calculate the percentage of the total that each cause represents

Add a cumulative percentage column to the table

Draw a Pareto chart plotting the causes on X-axis and cumulative

percentage on Y-axis. The Cumulative curve can be drawn to show the

cumulative percentage from all causes.

On the same chart, plot a bar graph with causes on X-axis and

percentage frequency on Y-axis. Analyze the diagram. Look for the break point on the cumulative percent

graph. It can be identified by a marked change in the slope of the graph.

This separates the significant few from the trivial many.

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Pareto Chart - Example

Category Number of

Complaints

Percentage Cumulative

Percentage

Cockroaches 962 43.2 43.2

Rooms temperature 505 22.7 65.9

Lighting 350 15.7 81.6

Storge space 127 5.7 87.3Stereo noise 97 4.4 91.7

Television broadcasting 83 3.7 95.4

Water 54 2.4 97.8

Towels 32 1.4 99.2

Furniture 15 0.8 100.00

TOTAL 2225

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Pareto Chart

Pareto Chart

BEQ/BOQ Complaints

Category

furn

towel

water

tv

stereo

store

light

temp

cock

NumberofComplaints

3000

2000

1000

0

Percent

100

50

0

350

505

962

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2. Cause-and-Effect Diagram

This diagram is also called as Fishbonediagram, Ishikawa diagram. The fishbone

diagram identifies many possible causes for

an effect or problem. It can be used tostructure a brainstorming session. It

immediately sorts ideas into useful categories.

The causeand-effect diagram is the

brainchild of Kaoru Ishikawa,

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Steps in Constructing a Cause and EffectDiagram

1. Write the issue (problem or process condition) on the center right side

of the Cause and Effect Diagram.

2. Identify the major cause categories and write them in the four boxes on

the Cause and Effect Diagram. You may summarize causes under

categories such as: Methods, Machine, Manpower, Materials,

Measurement, Environment

3. Brainstorm potential causes of the problem. As possible causes are

provided, decide as a group where to place them on the Cause and

Effect Diagram. It is acceptable to list a possible cause under more

than one major cause category.

4. Review each major cause category. Circle the most likely causes on

the diagram.

5. Review the causes that are circled and ask, Why is this cause?

Asking why will help get to the root cause of the problem.

6. Reach an agreement on the most probable cause(s).

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Cause-and-Effect Diagram

METHODS MACHINERY

MANPOWER

NEW OFFICEWORKINGMETHOD

MATERIALS

Office layout

Effect on other office

Remove old forms

Design new forms

Training

Teamwork

Re-designscreen

Effect Cause

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3. Check Sheet

It is also called as defect concentrationdiagram. 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. The function of a

check sheets is to present information in anefficient, graphical format.

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Steps in Creating a Check Sheet

Clarify the measurement objectives. Ask questions such as "What is

the problem?, "Why should data be collected?, Who will use the

information being collected?, Who will collect the data?

Create a form for collecting data. Determine the specific things that will

be measured and write this down the left side of the check sheet.Determine the time or place being measured and white this across the

top of the columns.

Collect the data for the items being measured. Record each occurrence

directly on the Check Sheet as it happens.

Tally the data by totaling the number of occurrences for each category

being measured.

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Check Sheet - Sample

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Application of Check Sheet

Distinguishing between fact and opinion (example: how does the

community perceive the effectiveness of the school in preparing

students for the world of work?)

Gathering data about how often a problem is occurring (example: how

often are students missing classes?)

Gathering data about the type of problem occurring (example: What isthe most common type of word processing error created by the

students-grammar, punctuation, transposing letters, etc.?)

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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4. Histogrm

Histograms provide a simple, graphical view of accumulated

data, including its dispersion and central tendency. In addition to

the ease with which they can be constructed, histograms provide

the easiest way to evaluate the distribution of data. A frequency

distribution shows how often each different value in a set of data

occurs. A histogram is the most commonly used graph to showfrequency distributions.

There are five types of Histograms based on five different types

of distributions and each indicates a very different type of

behavior. The various types of distributions are: Bell shaped

distribution Double-peaked distribution Plateau distribution

Comb distribution and Skewed distribution

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Histogram

Frequency Distribution

Class Lower limit Upper limit Frequency

1 35 38 1

2 38 41 2

3 41 44 4

4 44 47 5

5 47 50 8

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Histogram

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Application of 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 process is distributed

approximately normally.

When analyzing whether a process can meet the customers

requirements. When analyzing what the output from a suppliers process looks like.

When seeing whether a process change has occurred from one time

period to another.

When determining whether the outputs of two or more processes are

different.

When you wish to communicate the distribution of data quickly and

easily to others.

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5. Scatter Diagram

Scatter diagrams are used to investigate the possible relationship

between two variables that both relate to the same "event." A

straight line of best fit (using the least squares method) is often

included.

The scatter diagram also shows the pattern of relationship

between two variables. Examples of relationships are : Cutting

speed and tool life, Breakdowns and equipment age, Training

and errors, Speed and gas mileage, Production speed andnumber of defective parts

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Steps in Constructing a Scatter Diagram

Collect data for variables about the causes and effects.

Draw the causes on the X-axis

Draw the effect on the Y-axis

Plot the data pairs on the diagram by placing a dot at the

intersection of the X and Y coordinates for each data pair.

Interpret the scatter diagram for direction and strength

interpreting the direction.

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Interpretation of a Scatter Diagram

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Scatter Diagram - Example

Data collected by market research teamPrices of the

Commodity/Kg in Rs22 24 26 28 30 32 34 36 38 40

Demand for the

Commodity in Kg60 58 56 50 48 46 44 42 36 32

Fig 8.1.6. Scatter diagram

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6. Control Charts

The control chart is the fundamental tool of Statistical Process Control

(SPC), as it indicates the range of variability that is built into a system

(known as common cause variation). Thus, it helps determine whether

or not a process is operating consistently or if a special cause has

occurred to change the process mean or variance.

SPC4 is used to measure the performance of a process. It is the

application of statistical techniques to determine whether the output of a

process conforms to the product or service design. All processes are

subject to certain degree of variability. Usually variations are of twotypes:

Natural variations

Assignable variations.

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Components of Control Charts

A centerline, usually the mathematical average of all the samples

plotted.

Upper and lower statistical control limits that define the

constraints of common cause variations.

Performance data plotted over time.

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Construction of Control charts

Step 1:Draw the X-axis.

Step 2:Draw the Y-axis.

Step 3: Draw the Center-line

Step 4: Draw UCL and LCL

Step 5: Analyse and Interpret

Step 6: Determine Process Capability

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Types of Control Charts

Charts for Variables

Mean chart -X bar chart

Range chart - R chart

Charts for Standard Deviation

Chartxs for attributes

p chart

np chart

c chart

u chart

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Selection of Control Charts

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Application of Control Charts

To establish a state of statistical control

To monitor a process and signal when the process goes out of control

To determine process capability

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 toprevent specific problems or to make fundamental changes to the process

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7. Graphs

There are many kinds of graphs employed,depending on the shape desired and the

purpose of analysis. Bar graphs compare

values via parallel bars, while line graphs areused to illustrate variations over a period of

time. Circle graphs indicate the categorical

breakdown of values, and radar charts6 assistin the analysis of previously evaluated items

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Application of QC tools in Six-Sigma

Tool DMAIC Application

Pareto chart Anayse

Cause and effect diagram Analyse

Stratification Define

Check sheet Measure, Analyse

Histogram Measure, Analyse

Scatter diagram Analyse. Improve

Control charts Control

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The Seven New QC Tools

Affinity Diagram is otherwise known as KJ Method, which was, developed

by Jiro Kawakita.

Relations diagram is derived from cause and effect diagram. It shows

cause-and-effect relationships and helps to analyze the natural links

between different aspects of a complex situation

Systematic or Tree Diagram is nothing new but an adaptation from the

diagram Functional Analysis System (FAST) Technique in value

engineering

Matrix diagramis an adaptation from the Feasibility Ranking method

Matrix of value engineering, again.

Matrix Data Analysis is from the multivariate analysis method whose

calculations are a quite complex.

Arrow diagram is nothing but derivative from PERT (Programmeevaluation and review technique) and CPM (Critical Path Methodology)

Process Decision Programme Chart (PDPC) diagram is an adaptation from

the operations research methods.

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Application of New Seven Tools

Tool Name Utilization

Affinity Diagram Used to Organize abstract thinking about a

problem.

Relations Diagram Used for determining causalities among parts of a

problem.

Systematic/Tree Diagram Planning tool.

Matrix Diagram (many types) Used to organize knowledge in a matrix format;

sometimes includes intercellular relationships.

Matrix Data Analysis Method Principal components technique is performed on

matrix data.

Arrow Diagram Used to do 'what-fifing' on flow of process.

Process Decision Program Chart

(PDPC)

Determining which processes to use by evaluating

events and prospective outcomes.

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1. Affinity Diagram

It is also called as affinity chart, K-J method. The affinity diagram

organizes a large number of ideas into their natural relationships. This

method taps a teams creativity and intuition. It was created in the 1960s

by Japanese anthropologist Jiro Kawakita. It is a tool that gathers large

amounts of language data (ideas, opinions, issues) and organizes them

into groupings based on their natural relationships.

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Construction of a Affinity Diagram

Rapidly group ideas that seem to belong together.

It isn't important to define why they belong together.

Clarify any ideas in question.

Copy an idea into in more than one affinity set if appropriate.

Look for small sets. Should they belong in a larger group?

Do large sets need to be broken down more precisely?

When most of the ideas have been sorted, you can start to enter titles for

each affinity set.

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Application of Affinity Diagram

When you are confronted with many facts or ideas in apparent chaos

When issues seem too large and complex to grasp

When group consensus is necessary

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Affinity Diagram

Human resourceissues

Lack of standard

processesand measurement

Workplace culture Resources and tools

Too much turnover No standard systemsNot enough management

support

Not enough phonelines

Untrained staffNo measurement ofwhat is and what

isnt good serviceStaff feel unappreciated

Staff arent compensated

enough

Staff morale is low

Fig 8.2.1 Affinity diagram

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2. Relations Diagram

It is also called as interrelationship diagram or digraph, network diagram.

The relations diagram shows cause-and-effect relationships. Just as

importantly, the process of creating a relations diagram helps a group

analyze the natural links between different aspects of a complex

situation.

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Steps in Constructing Relations Diagram

State clearly the issue or problem. Write it on a card and stick it to the

center of a board.

Determine the factors related to the issue. Frequently these will be the

headers from a previously completed affinity diagram. Place cards

containing these factors in a circle around the issue card.

Determine if cause-effect relationships exist between any of the cards. If

so, draw an arrow from the "cause" card to the "effect" card. Do this for

all cause/effect relationships that you can find.

Analyze the relationships. Cards that have most arrows going from them

tend to be root causes. Cards that have most arrows going to them areroot effects.

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Relations Diagram

Customer focus

Lack of focus

Indequate training time

No standard TQM method

Responsibility not clear

Lack of knowledgeof quality

improvement Lack of communicationof information

Confusion of committees

withoutorganization

Lack of TQMcommitment bytop managers

Lack of quality strategy

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Use of Relations Diagram

Identifying key or driver issues from a list of important issues.

Identifying the most important problems for solution when the number of

problems exceeds the resources available to solve all of them.

Identifying the root cause of existing problems.

Identifying key factors needed to make a decision when there is

insufficient information available to make a data-driven decision.

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3. Systematic or Tree Diagram

It is also called as systematic diagram, tree analysis, analytical tree,

hierarchy diagram. Tree Diagram is a technique for mapping out full rangeof paths and tasks that need to be done in order to achieve a primary goal

and related sub goals.

Such a diagram reveals in a simple way with clarity not only the magnitude

of the problem but also helps to arrive at methods, which are to be pursued

to achieve the results. In other words, it serves the purpose of developing

the essential means to achieve an objective or goal.

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Tree Diagram

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Use of Tree Diagram

Developing a sequence of steps that depend on each other that form the

solution to a problem.

When it is known that the implementation of some task will be a complex

sequence.

When serious consequences can occur as the result of missing a key step

in implementing the solution to a problem

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4. 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.

A Matrix Diagram consists of a number of columns and rows whose

intersections are checked up, to find out the nature and strength of theproblem which help us to arrive at key ideas and analyzing the relationship

or its absence at the intersection and finding an effective way of pursuing

the problem solving method.

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Types of Matrix Diagram

An L-shaped matrix: It relates two groups of items to each other (or one

group to itself).

A T-shaped matrix: It 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: It relates three groups of items. Each group is related to

the other two in a circular fashion.

A C-shaped matrix: It relates three groups of items all together

simultaneously, in 3-D.

An X-shaped matrix: It relates four groups of items. Each group is related to

two others in a circular fashion.

A roof-shaped matrix: It relates one group of items to itself. It is usuallyused along with an L- or T-shaped matrix.

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Steps in Constructing a Matrix Diagram

Determine the factors that are important for making a correct selection or

assignment.

Select the type of matrix to be used. L-shaped matrices are used for two-

factor comparisons; T-shaped are used for 3-factor comparisons in that

display indirect and direct relationships; Y-shaped are used for 3-factor

comparisons showing direct relationship only.

Select the relationship symbols to be used.

Complete the proper matrix using the appropriate factors and symbols.

Examine the matrix and draw the appropriate conclusion.

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Industrial Applications of Matrix Diagram

It is often used in deploying quality requirements into counterpart

(engineering) characteristics and then into production requirements.

Establish idea conception points for the development and improvement ofsystem products

Achieve quality deployment in product materials

Establish and strengthen the quality assurance system by linking certifiedlevels of quality with various control functions

Reinforce and improve the efficiency of the quality evaluation system

Pursue the causes of non conformities in the manufacturing process

Establish strategies about the mix of products to send to market byevaluating the relationships between the products and market situations.

l

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5. Matrix Data Analysis

Matrix Data Analysis is a multivariate analysis technique called 'Principal

Component Analysis'. This technique quantifies and arranges data

presented in a Matrix Diagram, to find more general indicators that would

differentiate and give clarity to large amount of complexly intertwined

information. This will help us to visualize properly and get an insight into

the situations.

This diagram is used when the matrix chart does not provide sufficiently

detailed information. This is the only method within the New Seven that is

based on data analysis and gives numerical results.

Characteristics of Matrix Data Analysis

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Characteristics of Matrix Data AnalysisDiagram

The matrix analysis method qualifies and arranges matrix diagram data so

that the information is easy to visualize and comprehend.

The relationships between the elements shown in a matrix diagram are

quantified by obtaining numerical data for intersection cells.

Of the seven new QC tools, this is the only numerical analysis method. The

results of this technique, however, are presented in diagram form.

One major technique that this method also utilizes is known as principal-

components analysis.

U f M i D A l i Di

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Use of Matrix Data Analysis Diagram

Analyze production processes where factors are complexly intertwined

Analyze causes of nonconformities that involve a large volume of data

Grasp the desired quality level indicated by the results of a market

survey

Classify sensory characteristics systematically

Accomplish complex quality evaluations

Analyze curvilinear data

6 A Di

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6. Arrow Diagram

It is also called as activity network diagram, network diagram, activity chart,

node diagram, 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.

The arrow diagram lets you calculate the critical path of the project. This

is the flow of critical steps where delays will affect the timing of the entire

project and where addition of resources can speed up the project.

St i C t ti A Di

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Steps in Constructing Arrow Diagram

Select a team that is knowledgeable about the project, its tasks, and sub

tasks.

Record all of the tasks and sub tasks necessary to the completion of the

project.

Sequence the tasks.

Assign time duration to each task.

Calculate the shortest possible implementation time schedule using the

critical path method.

Calculate the earliest starting and finishing times for each task.

Locate tasks with slack (extra) time and calculate total slack.

Update the schedule as the project is being completed.

A li ti f A Di

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Application of Arrow Diagram

Understanding and managing a complex project or task.

Understanding and managing a project that is of major importance to the

organization, and the consequences of late completion are severe.

Understanding and managing a project in which multiple activities must

take place and be managed simultaneously.

Explaining the project status to others.

Plan and follow up QC inspections and diagnostic tests

7. Precision Decision Programme Chart

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7. Precision Decision Programme Chart(PDPC)

The Process Decision Program Chart (PDPC)9 is a very useful and

powerful method to overcome a problem or a goal to be achieved which

are not familiar. With the help of PDPC we can map out all the

conceivable events or contingencies that can occur in the

implementation stage and also find out feasible counter measures to

overcome these problems.

Ch t i ti f PDPC

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Characteristics of PDPC

The PDPC diagram is a simple graphical tool, which can be used to mitigate

risk in virtually any undertaking The PDPC method helps determine, which processes to use to obtain

desired results by evaluating the progress of events and the variety of

conceivable outcomes.

Implementation plans do not always progress as anticipated. When

problems, technical or otherwise, arise, solutions are frequently not

apparent. The PDPC method, in response to these kinds of problems, anticipates

possible outcomes and prepares countermeasures that will lead to the best

possible solutions.

Establish an implementation plan for management by objectives

Establish an implementation plan for technology-development themes

Establish a policy of forecasting and responding in advance to majorevents predicted in the system

Implement countermeasures to minimize non-conformities in the

manufacturing process to set up and select adjustment measures for

negotiating process

St i C t ti A PDPC Di

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Steps in Constructing A PDPC Diagram

Select a team that is familiar with the process and possible contingencies.

Typically, this will be a group that has been close to the effort or a similar

effort.

Determine the flow of the activities of the plan and place them on a flow

chart or sequence.

Construct a tree diagram, placing prerequisite activities in a time

sequence. This can be done either a horizontal or vertical format.

At each step, ask, "What could go wrong here?" and place that

contingency on the chart.

Determine plausible explanations/solutions to each problem identified

above and place the solution on the chart.

Application of PDPC Diagram

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Application of PDPC Diagram

Exploring all of the possible contingencies that could occur in the

implementation of any new or untried plan that has risks involved.

Implementing a plan that is complex and the consequences of failure are

serious.

Implementing a plan in which there is generally a time constraint for

implementing a plan so that insufficient time is available to deal with

contingent problems as they occur.