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“Have You Found
The ‘Root Cause’ Yet?”- A New Spin to Root Cause Analysis
Gary Jing, PhD, MBBNov 14, 2006
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 2
The Tie Between the Speaker & the Topic
MS in Reliability & Applied StatisticsMS in Reliability & Applied Statistics
PhD in IEPhD in IE
Editorial Review Board of Editorial Review Board of Six Sigma Forum MagazineSix Sigma Forum Magazine
Founding MBB at Seagate TCO, the worldFounding MBB at Seagate TCO, the world’’s largest disc drive s largest disc drive
design center (1998 design center (1998 -- 2005)2005)
2 patents in disc drive modeling generated from his Sigma work2 patents in disc drive modeling generated from his Sigma work
Sr. Mgr., Global Lean Sigma / MBB, Entegris (2005 Sr. Mgr., Global Lean Sigma / MBB, Entegris (2005 -- present)present)
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 3
Personal Philosophy – Striving for Balance
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 4
Topics to be Covered
The Tie Between the Speaker & the Topic
The Mindset of Infinite Chain of Causation (New Spin 1)
The Role of Root Cause Analysis (RCA) in Six Sigma
Methodology
Popular RCA Tools Used in Six Sigma
– Differentiating & Prioritizing Causes (New Spin 2)
Summary
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 5
Cause-Effect Relationship
CAUSEEvents/conditions
that led tothe problem
A PROBLEM WHICHHAS OCCURED
EFFECTSymptoms that
provide evidenceof the problem
ACTION
CORRECTIVE
Eliminates the
CAUSE
of a problem
ADAP
TIVE
Lim
its th
eEF
FECT
of a
prob
lem
or d
evia
tion
Dave Wessel, “An Ounce of Prevention”, Quality Progress, Dec, 1998
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 6
Cause-Effect Principle – Chain of Causation
The same thing is both a cause and an effect at the same time.
Causes and effects are part of an infinite continuum of causes.
Injury caused by Fall
Fall caused by Wet Surface
Wet Surface caused by Leaky ValveLeaky Valve caused by Seal FailureSeal failure caused by Poor Maintenance
EFFECTS CAUSES
Reference: Apollo Root Cause Analysis, Dean L. Gano5 Why’s...
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 7
The Concept of Infinite Chain of Causation
Widely seen in philosophical level of discussion. e.g., Hegel’s philosophy.
“An important feature of causality is the continuity of the cause-effect connection. The chain of causal connections has neither beginning nor end. It is never broken... And no one can say where this chain began or where it ends. It is as infinite as the universe itself. There can be neither any first (that is to say, causeless) cause nor any final (i.e., inconsequential) effect. If we were to admit the existence of a first cause we should break the law of the conservation of matter and motion. And any attempt to find an ‘absolutely first’ or ‘absolutely final’ cause is a futile occupation, which psychologically assumes a belief in miracles.” - A. Spirkin, Dialectical Materialism
Applied by Dean L. Gano in Apollo Root Cause Analysis - A New Way Of Thinking, He warned that “because this book challenges conventional wisdom, it may not validate your existing belief system". -
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 8
Root Cause Analysis (RCA)
Challenge!!!: With infinite layers of Cause and Effect, how do we know where to stop and conclude we have reached “Root Cause”?
– Case study 1: Jefferson Memorial
“Have you found ‘the root cause’?”– The term “root cause” is somewhat misleading– A so-called “root cause” is subjectively chosen to serve as
the “root cause”
RCA Theme– Continuously migrate the focus to upstream causes– Keep asking “why” like a 2-year old
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 9
So, Where to Stop?- To conclude we have reached “Root Cause”?
Usually the lowest cause in a chain at which we have some capability to cause the break is chosen as the root cause.
The lowest level at which it is within our capability to unilaterally control, or to influence, changes to the cause
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 10
Three Important Principles . .
Where to stop? Where to stop? -- The trick is The trick is not to find the not to find the ““truetrue”” root causeroot cause per se. per se.
-- The trick is where to stop and treat what you have as The trick is where to stop and treat what you have as the root cause. That wisdom is what differentiates an the root cause. That wisdom is what differentiates an adult from a 2adult from a 2--year old; an expert from a novice. year old; an expert from a novice.
– The bottom-line is High ROI – low cost with high return.
-- Three tips:Three tips:– Leverage Point Thinking– Pareto Principle– Span of Control / Sphere of Influence
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 11
Leverage Point Thinking & Pareto
How Do You Turn the Ship?Knowing the leverage points is critical for determining priorities and strategies for improvement
Vital Few
Trivial Many
Pareto Principle 80% of the problems are caused by only about 20% of the contributing factors.
Case study 2: The “Snow Map”
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 12
Span of Control / Sphere of Influence
SPHERE OF INFLUENCE(Influence or persuasion only)
SPAN OF CONTROL(Full authority)
Before we begin, we must establish the context in which the Cause-Effect will be used.
Span of Control - areas where we have a high degree of control over parts or functions, virtually complete authority to change anything
Sphere of Influence - areas where we can influence things to varying degrees but don’t have direct control.
Outside Environment - where we have neither control nor influence
OUTSIDE, UNCONTROLLEDENVIRONMENT
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 13
The Role of RCA in Six Sigma Methodology- DMAIC Process (Roadmap)
Define Define the problem; Establish project charter (goals, scope, team & timeline)
Measure Identify customer requirements / Critical To Quality (CTQ’s)Translate into measurable Key Process Output Variables (KPOV’s) Verify measurement system Establish present capabilityIdentify any factors / Key Process Input Variables (KPIV’s) that may
potentially affect the outputs (KPOV’s) through process mapping Establish high potential suspects (hypotheses) through cause-effect
analysis (subjective analysis using experience & expertise)
Analyze Validate the suspects / hypotheses using existing data through statistical testing (objective analysis)
Reduce list of high potential KPIV’s to vital fewImprove Generate improvement ideas using soft tools (subjective)
Use DOE to generate new data when no existing data available and to optimize & validate outputs (objective)
Control Put in place permanent controls
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 14
Five Types of Cause-Effect Analyses
1. Is / Is not Comparative Analysis2. 5 - Whys3. Fishbone Diagram (Cause-effect Diagram) - Traditional
approach to brainstorming and diagramming Cause-Effect relationships. Good tool when there is one primary effectbeing analyzed.
4. Cause & Effect Matrix - Used to relate and prioritize X’s to customer CTQ’s through numerical ranking. Good tool when there is more than one primary effect being analyzed.
5. Root Cause Tree - A problem analysis diagram that begins with undesirable effects and works back to root causes and core problems.
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 15
Cause-Effect Analysis
I keep six honest serving men,
They taught me all I knew,
Their names are What and Why and How
and Where and When and Who
Rudyard Kipling
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 16
Is / Is Not Comparative Analysis
How many objects with the defect? How many defects per object? Size of defect? Trend?
Size
When was the defect first observed? When since then? When in the product life cycle?
When
Geographically? Physically on the part?
Where
What similar objects could have the defect but do not? What other defects could be observed but are not?
What is the specific object has the defect? What is the specific defect?
What
Differences and Changes
Is NotIs
Statement:Problem
Where, when and what size could the defect have been but it was not?
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 17
Fish Bone Diagram
- Focusing on single effect with simplecause-effect relationships
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 18
“Fishbone” Cause-Effect DiagramAdvantages
Helps organize and relate factorsProvides a structure for brainstormingInvolves everyone
DrawbacksMight become very complexRequires patienceDoes not rank the causes in an if- thenmanner
MethodsMaterials
Machinery Manpower
C/N/X
C
C
C
N N
NNN
C
C
Problem/Desired
Improvement
C = Control FactorN = Noise FactorX = Factor for DOE (chosen later)
Opportunity:H: HighM: MediumL: Low
Controllability:C: Within controlI: Have influenceN: No influence
New spin 2: Categorizing / labeling Causes:
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 19
Use Cause and Effect Diagram to Single Out Variation Sources within the “5M’s + E”
Use Cause and Effect Diagram to Single Out Variation Sources within the “5M’s + E”
Man
MethodsMachine
Materials Measurement
Five Key Sources of Variation
Environment+
Product: The 5M’s
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 20
You can merge the cause and effect with the affinity diagram by placing your Post-Its directly onto the fish. This helps reduce the number of headings generated.
You can merge the cause and effect with the affinity diagram by placing your Post-Its directly onto the fish. This helps reduce the number of headings generated.
People
ProceduresPolicies
Place Measurement
Five Key Sources of Variation
Environment+
Transactional or Process: 4P’s + M&E
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 21
Fishbone Example #2
HighNumber o finv en to ryad ju stments
Env iro nmen t
Retu rn s
Receip ts
P ro cedu res
Data En try
C y c le C o un ts
w rong counts
N o D ata av a ilable
B ad T y ping
A ccuracy of counts
Lack of tra ining
N ot be ing done
Line shut dow n
ov er sta ted inv entory
G oods issue not done
incorrectquantity
w rong partsrece iv ed
excessinv entory
w ork orderv ariance
N o I nv entory bylocation
Lack of S pace
em pl o ye esTemp
o rd e rswo rk
Ope n
Requ is iti o ns
Inventory AdjustmentsAGB project: New spin 2: Differentiate causes.
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 22
Weaknesses of the Fishbone
Although the “fishbone” cause-effect diagram has been very popular over the years, it has some inherent weaknesses:
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Root Cause Analysis - ASQGary Jing 11/14/06 Slide 23
Cause and Effect Matrix
- To evaluate the impact of a group of causes on a group of effects
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 24
Cause and Effect Matrix
Rating of Importance to
Customer1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Req
uire
men
t
Total
Process Step Process Input
1 02 03 04 05 06 07 08 09 010 011 012 013 014 015 016 017 018 019 020 0
0
Total 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Lower Spec
TargetUpper Spec
Cause and Effect Matrix
C&E Matrix.xls
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 25
C-E Matrix: Example
10 6 9 8
1 2 3 4 5 6
Effic
ienc
y
Com
mon
ality
Yiel
d (a
ccur
acy)
Cha
nge
Impl
emen
tatio
n
1 Customer Input 8 6 8 8 252 11.36%2 Equipment Specs 8 5 10 8 264 11.90%3 Bill of Materials 7 5 10 5 230 10.37%4 # of Revisions 8 6 10 8 270 12.17%
5Label Documentation 8 2 8 9 236 10.64%
6 CC Drawings 5 3 2 2 102 4.60%7 Pre-CCP Metting 5 5 2 2 114 5.14%8 Ownership 8 10 8 8 276 12.44%9 Approval Cycles 8 8 5 8 237 10.69%
10 AMK Delays 8 8 5 8 237 10.69%
2218
Rating of Importance to Customer
TOTAL %
PROCESS INPUTS Sometime it’s
used to rank
Fishbone inputs.
Customer ECO Throughput ReductionCustomer ECO Throughput Reduction
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 26
Cause-Effect Matrix Analysis Example
0.1 0.5 1 3 5 1 -2 1 -2
Material
# of adjustm
ent entry / Total
Added quantity
/ total
Substracted
quantity / total
Added $ / Total
Substracted $ / Total Overall
Added quantity/ consum
ption
Substracted
quantity/ consum
ption
Added $/
consumption
Substracted $ / consum
ption
Rank without Consum
ption Info
Rank by Substracted $
Overall Rank
830R25 0.001 0.000 0.001 0.000 0.027 0.138 -2.840 -2.840 11 4 1225 0.001 0.000 0.036 0.000 0.013 0.102 0.028 -2.807 0.028 -2.807 18 17 2
7500-0585-03 0.007 0.020 0.037 0.003 0.004 0.076 0.358 -0.317 0.357 -0.316 28 51 301-001638 0.004 0.000 0.003 0.042 0.184 1.050 0.011 -0.036 0.011 -0.036 1 1 401-006154 0.005 0.004 0.010 0.008 0.014 0.108 0.183 -0.244 0.157 -0.209 15 15 5
4002-5973-02 0.002 0.002 0.006 0.004 0.012 0.081 0.102 -0.202 0.102 -0.202 24 20 601-004488 0.003 0.001 0.005 0.009 0.061 0.337 0.027 -0.134 0.027 -0.134 2 2 7
8100-0100-01 0.012 0.009 0.000 0.067 0.000 0.206 0.564 0.564 7 403 8200 0.003 0.009 0.034 0.005 0.013 0.117 0.071 -0.135 0.071 -0.135 13 18 9
7500-0585-07 0.003 0.024 0.017 0.008 0.004 0.071 0.258 -0.092 0.258 -0.092 30 52 101032-047 0.018 0.052 0.000 0.014 0.000 0.069 0.570 0.569 32 403 11PKG-782 0.017 0.131 0.000 0.009 0.000 0.096 0.530 0.530 20 403 12
01-009871 0.002 0.002 0.005 0.018 0.030 0.212 0.072 -0.083 0.071 -0.084 6 3 1301-009644-17C02 0.001 0.000 0.001 0.006 0.017 0.103 0.047 -0.107 0.046 -0.103 17 11 14
9700-7036-01 0.003 0.004 0.002 0.049 0.018 0.241 0.141 -0.037 0.141 -0.037 4 8 1501-001651 0.003 0.003 0.005 0.015 0.020 0.152 0.073 -0.070 0.073 -0.070 9 7 16
160 0.001 0.000 0.001 0.000 0.016 0.079 -0.095 -0.094 25 13 1701-018514 0.016 0.034 0.000 0.073 0.000 0.238 0.203 0.203 5 403 1801-021524 0.001 0.001 0.003 0.008 0.016 0.109 0.062 -0.069 0.047 -0.071 14 12 1901-009897 0.003 0.002 0.008 0.003 0.011 0.076 0.029 -0.076 0.029 -0.077 27 21 2001-021554 0.001 0.000 0.002 0.001 0.012 0.069 0.013 -0.073 0.014 -0.087 31 19 21
Inpu
t Var
iabl
es -
Mat
eria
ls
Output Variables that Reflect the Impact of Adjustment
RankWeight
AGB project: Inventory Accuracy
Sometime the ranking can be objective, data driven.
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 27
Root Cause Tree (RCT)
- For more complicated cause - effect relationships (causes may be dependent on each other)
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 28
Example of RCT
AGB project: Potting Leaks
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 29
Distinguishing Undesirable Effects From Neutrals
Two “Rules of Thumb”1. What bearing does the effect have on the system goal?2. Does the effect pass the “So What” test?
UDE’s are negative on their own meritNo further explanation why is neededEffects are negative at face value
“We lost money last quarter”*Undesirable Effects
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 30
Rules, Guidelines
Clarity: Someone stating a cause-effect relationship must take care to ensure that others will:
– Understand the individual words
– Comprehend the meaning of the idea
– See a clear connection between cause and effect
Purpose: To help us construct our own logical relationships and to evaluate the logic of others
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 31
Rules, GuidelinesCausality Existence– Tests the connections– One basic criterion: Does the proposed cause really produce the
observed effect?– The Cause-Effect relationship must be direct and unavoidable– If not clear - keep looking, you missed something
I can’t buy a new car
I can’t buy a new car
I have lessdisposable income
Taxes areraised
Taxes areraised
?
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 32
Rules, Guidelines
Cause Insufficiency– Be sure you have identified and included all of the major contributing
causes– To be contributing, causes must depend on one another– Two questions:
• Is the cause alone enough to deliver the effect?• If I take away one of the causes, will I still have the effect?
I leave mybook outdoors
My book gets wet
I leave mybook outdoors
My book gets wet
It rainstoday
“AND”
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 33
Rules, Guidelines
Additional Cause– Consider all possible independent causes– A cause may consist of several independent causes, any of
which would have produced the effect– Each independent cause would increase the magnitude of
the observed effect
Bills areignored
Accounts receivableare too high
Paymentsare late
Bills arepartially paid
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 34
Rules, Guidelines
Circular reasoningThe effect is the rationale for the existence of the cause– More common in conversation than on graphs– Example:
• The fisherman brought home several large fish• WHY? - The fishing was good• HOW DO YOU KNOW? - He brought home several large fish, didn’t he?
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 35
Example RCTCustomer suffered a corrosion
problem, meantime they tested a surge of sulfate with our product. They suspect it’s the primary contributor and demand for the root cause and control.
A. Understand the meaning and “reliability”
of customer data
The readingsare the
calculated Sulfate
concentration of product /
resin?(surface
only?) or the sulfate
concentration of test
coupon / water? L,N
Correlation doesn’t mean causation. Is Sulfate really the
primary contributor?(Otherwise it may not help the problem.) – Need to work with
customer and their data. M,I
What’s the repeatability
and reproducibilityof customer
data. L,N
What’s the Correlation
between our data and their data. L,N
B. Internal measurement of
Sulfur related anion
C. SRA originated from original material
D. SRA introduced during manufacturing
process
B1. Where do we measure
SRA, R&R. H,C
B2. Resin test. M,IB3. Test
prime product?
H,C
B4. Test cleaned product?
H,C
B5. Test / monitor cleaning
solution? H,C
B6. Air quality. M,C
E. SRA introduced after manufacturing
C1. Lot to lot
variation. H,N
SRA transform during
manufacturing. M,I
During molding.
L,I
During Cleaning.
L,CExposing to air. M,N
Cross contamination
when lines shift products.
L,I
Resin absorb SRA from air. M,C
Outside cleanroom
Inside cleanroom
Parts absorb SRA from air inside cleanroom. M,C
Bag contamination.
L,C
E1. Product absorb SRA
overtime.H,I
Contamination through leaking
bag. L,I
SRA transform overtime.
M,N
Product release
SRA overtime.
L,I
Opportunity:H: HighM: MediumL: Low
Controllability:C: Within controlI: Have influenceN: No influence
Color code:• Being studied• Should investigate
Cleaning removes /
absorb SRA. M,C
B7. Sample size. M,I
(SRA – Sulfur related anion)
Root Cause Analysis - ASQGary Jing 11/14/06 Slide 36
Summary
New Spin 1: The Mindset of Infinite Chain of Causation
The Role of Root Cause Analysis (RCA) in Six Sigma
Methodology
Popular RCA Tools Used in Six Sigma – Is / Is not analysis– Fishbone Diagrams (Cause-effect Diagram)– C&E Matrix– Root Cause Tree
New Spin 2: Differentiating & prioritizing causes