Cause an Effect Diagram

8/15/2019 Cause an Effect Diagram

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Basic Tools for Process Improvement

Module 5

CAUSE-AND-EFFEDIAGRAM


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CAUSE-AND-EFFECT DIAGRAM VIEW

What Is a Cause-and-Effect

Diagram?

A graphic tool that helps identif

sort, and display possible causes

a problem or quality characteristic.

Benefits of Usinga Cause-and-Effect Diagram

• Helps determine root causes

• Encourages group participation• Uses an orderly, easy-to-read forma

• Indicates possible causes of variatio



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Basic Layout of Cause-and-Effect Diagrams

CAUSE A

CAUSE D

CAUSE C

CAUSE B

EFFECT

Step 1 - Identify and Define the Eff

• Decide on the effect to examine

• Use Operational Definitions

• Phrase effect as

>positive (an objective) or



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Step 2 - Using a chartpack positioned so that everyone can see it, d

SPINE and c reate the EFFECT box.

! Draw a horizontal arrow pointing to the right. This is the spine.

! To the right of the arrow, write a brief description of the effect or outcwhich results from the process.

EXAMPLE: The EFFECT is Poor Gas Mileage (Viewgraph 5).

! Draw a box around the description of the effect.

Step 3 - Identify the main CAUSES contributing to the effect being s

These are the labels for the major b ranches of your diagram and becocategories under which to list the many causes related to those catego

! Establish the main causes, or categories, under which other possiblewill be listed. You should use category labels that make sense for thyou are creating. Here are some commonly used categories:

> 3Ms and P - methods, materials, machinery, and people> 4Ps - policies, procedures, people, and plant> Environment - a potentially significant fifth category

! Write the main categories your team has selected to the left of the efsome above the spine and some below it.

! Draw a box around each category label and use a diagonal line to fobranch connecting the box to the spine.

EXAMPLE: Viewgraph 6 uses the 3Ms and P to start developing thwe began in Step 2.


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Step 2 - Fill in the Effect Box an

Draw the Spine

POORGAS

MILEAG

Step 3 - Identi fy Main Categor ie

POO

GA

MILEA

METHODS MACHINERY



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Step 4 - For each major branch, identify o ther specific factors wh ic

the CAUSES of the EFFECT [Ref. 5, p. 20].

Identify as many causes or factors as possible and attach them assubbranches of the major branches.

EXAMPLE: The possible CAUSES for Poor Gas Mileage are listedappropriate categories in Viewgraph 7:

Fill in detail for each cause. If a minor cause applies to more than oncause, list it under both.

Step 5 - Identify increasingly m ore detailed levels of causes and coorganizing them under related causes or categories. You can do asking a series of why questions.

EXAMPLE: We’ll use a series of why questions to fill in the detailed levone of the causes listed under each of the main categories.

Q: Why was the driver USING THE WRONG GEAR? A: The driver couldn't hear the engine.

Q: Why couldn't the driver hear the engine? A : The radio was too loud. A : Poor hearing

Q: Why were the TIRES UNDERINFLATED? A: No record of tire pressure A: Difficult air stems

Q: Why were the air stems difficult? A : Poor design

Q: Why was MAINTENANCE POOR? A: Lack of money A: No awareness

Q: Why was WRONG OCTANE GAS used? A: Didn’t know recommended octane


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Step 4 - Identi fy Causes Inf luencithe Effect

POO

GA

MILEA

METHODS MACHINERY

PEOPLE MATERIALS

DRIVE

TOO FAST

USE WRONGGEARS

CARBURETOR ADJUSTMENT

UNDERINFLATEDTIRES

POORMAINTENANCE

POORDRIVING HABITS

IMPROPERLUBRICATION

WRONGOCTANE

GAS

Step 5 - Add Detailed LevelsStep 6 - Analyze the Diagram

ALWAYSLATE

POO

GA

MILEA

METHODS MACHINERY

DRIVETOO FAST

USE WRONGGEARS

CARBURETOR ADJUSTMENT

UNDERINFLATEDTIRES

WRONGOCTANE

GAS

IMPATIENCE

POOR HEARING

RADIO TOOLOUD

CAN’T HEARENGINE

MECH. DOESN’T KNOWCORRECT ADJUSTMENT

PROCEDURES

FUEL MIXTOO RICH

DIFFICULT AIR STEMS

POOR DESIGN

NO RECORD OFTIRE PRESSURE

POORTRAINING

NO OIL

POORMAINTENANCE



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NOTE: You may need to break your diagram into smaller diagrams if one has too many subbranches. Any main cause (3Ms and P, 4Ps, or a categohave named) can be reworded into an effect.

Step 6 - Analyze the diagram . Analysis helps you identify causes that wfurther investigation. Since Cause-and-Effect Diagrams identify only pocauses , you may want to use a Pareto Chart to help your team determicause to focus on first.

Look at the “balance” of your diagram, checking for comparable levefor most of the categories.

> A thick cluster of items in one area may indicate a need for furthe> A main category having only a few specific causes may indicate a

further identification of causes.> If several major branches have only a few subbranches, you may

combine them under a single category.

Look for causes that appear repeatedly. These may represent root c

Look for what you can measure in each cause so you can quantify thof any changes you make.

Most importantly, identify and circle the causes that you can take act

EXAMPLE: Let's analyze the diagram we have been constructing.

> The level of detail is pretty well balanced.

> No causes are repeated.

> Poor Maintenance appears to be a cause for which you could devmeasurements.

> Moreover, Poor Maintenance appears to be a cause that you canaction on. It is circled in Viewgraph 8 to earmark it for further inv


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How can we practice what we’ve learned?

Some practical exercises will enable your team to practice constructing aanalyzing Cause-and-Effect Diagrams. The first exercise is sketched outWhen you have completed that, you can try your hand with one or two othfrom the list that follows the detailed exercise.

DETAILED EXERCISE: Construct a Cause-and-Effect Diagram to the causes of computer dow ntime in your organization.

! Draw a horizontal arrow to the right, write the effect (computer dowdraw a box around it.

! Identify the main causes contributing to the effect.

! Draw boxes around the main categories and connect the boxes to

horizontal arrow with diagonal arrows to form the fishbone.

! For each branch, identify specific factors which may be the causeseffect.

! Add increasingly detailed levels of causes.

! Analyze the diagram and circle causes that you can take action on

Viewgraph 9 shows one way the completed diagram could be drawn.

OTHER EXERCISE TOPICS:

> What is causing the poor state of readiness of the fire control syste

> What is causing our ship to drag anchor in heavy weather?

> What is causing us to fail our corrosion-control inspections?

> What factors affect the proper disposal of recyclable material on the

> What things do we need to consider in planning a perfect meeting?


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CAUSE-AND-EFFECT DIAGRAM VIEWGR

Example of How the Cause-and-Effect Diagram

Could Be Constructed for the Detailed Exercise

COMPUT

DOWNT

SOFTWARE USERS

HARDWARE ENVIRONMENT

FAULTYDESIGN

FAULTY

MEDIA

MISAPPLICATION OF SOFTWARE

INADEQUATEPOWER

TEMPERATURE GRADIENTS

MECHANICALSHOCK

HUMIDITY

CORROSION

INADEQUATEDOCUMENTATION

FAULTYINSTALLATION

POWERFLUCTUATIONS

COMPONENTFAILURE

LACK OFTRAINING

ABUSE OFHARDWARE

MISUSE OFHARDWARE

FAULTYCOMPONENT



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REFERENCES :

1. Brassard, M. (1988). The Memory Jogger, A Pocket Guide of Tools foContinuous Improvement, pp. 24 - 29. Methuen, MA: GOAL/QPC.

2. Department of the Navy (November 1992). Fundamentals of Total QuLeadership (Instructor Guide), pp. 6-25 - 6-29. San Diego, CA: Navy Research and Development Center.

3. Department of the Navy (September 1993). Systems Approach to ProImprovement (Instructor Guide), pp. 5-15 - 5-27. San Diego, CA: OUSQuality Leadership Office and Navy Personnel Research and DevelopCenter.

4. Department of the Navy (November 1992). Team Skills and ConceptsGuide), pp. 5-47 - 5-56. Washington, DC: OUSN Total Quality Leade

5. Ishikawa, Kaoru (1968). Guide to Quality Control. Tokyo, Japan: AsiProductivity Organization.

6. U.S. Air Force (Undated). Process Improvement Guide - Total QualityTeams and Individuals, p. 33. Air Force Electronic Systems Center, AMateriel Command.


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C A U S E -A

ND-E F F E C T DI A GRA M

V I E W GRA P H1

Wh a t

I s a C a u s e- an d -E f f e c t

Di a g

r am?

A gr a ph i c t o ol t

h a t h el p s

i d en t i f y ,

s or t , an d d i s pl a y

p o s s i b l e c a u s e s of

a pr o b l e

m or q u al i t y c h ar a c t er i s t i c .


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C A U S E -A ND-E F F E C T DI A GRA M

V I E W GRA P H2

B en ef i t s

of U s i n

g

a C a u

s e- an d -E f f e c t Di a gr am

• H el p s d e

t er mi n er o o t c a u s e

s

• E n c o ur a

g e s gr o u p

p ar t i c i p a

t i on

• U s e s an

or d er l y , e

a s y - t o-r e a d f or m a t

• I n d i c a t e s p o s s i b l e

c a u s e s o

f v ar i a t i on

• I n c r e a s e

s pr o c e s s

k n owl e d g e

• I d en t i f i e s ar e a s f or c ol l e c t i n g d a t a


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V I E W GRA P H 3

B a s i c L

a y o u t of

C a u s

e- an d -E f f e c t Di a

gr am s

C A U S E A

C A U S E

D

C A U S E

C

C A U S E B

E F F E C T


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V I E W GRA P H4

S t e p1 -I d

en t i f y an

d D ef i n e

t h eE f f e

c t

• D e c i d e

on t h e ef f e c t t o ex a

mi n e

• U s e O p

er a t i on al

D ef i ni t i on s

• P h r a s e

ef f e c t a s

> p o s i t i v e ( an o b j e c t i v e ) or

> n e g a t i v e ( a pr o

b l em )


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V I E W GRA P H 5

S t e p2 -F i l l i n t h

eE f f e c t

B ox an d

Dr aw t h

e S pi n e

P O OR

GA S

MI L E A GE


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V I E W GRA P H 6

S t e p 3 -

I d en t i f y

M ai n C a

t e g or i e s

P O OR

GA S

MI L E A GE

ME T H OD S

MA C HI NE

RY

P E OP L E

M

A T E RI A L S


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V I E W GRA P H7

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RI V I N GHA B I T S

I MP R

OP E R

L UB RI C A T I ON

WR O

N G

O C T

A NE

GA S


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V I E W GRA P H

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V I E W GRA P H

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Cause an Effect Diagram