QUALITY BASICS
Root Cause Analysis
For Beginners
by James J. Rooney and Lee N. Vanden Heuvel
R
oot cause analysis (RCA) is a process
designed for use in investigating and categorizing the root causes of events with safety, health, environmental, quality, reliability and
production impacts. The term “event” is used to
In 50 Words
Or Less
• Root cause analysis helps identify what, how
and why something happened, thus preventing
recurrence.
• Root causes are underlying, are reasonably
identifiable, can be controlled by management
and allow for generation of recommendations.
• The process involves data collection, cause
charting, root cause identification and recommendation generation and implementation.
generically identify occurrences that produce or
have the potential to produce these types of consequences.
Simply stated, RCA is a tool designed to help
identify not only what and how an event occurred,
but also why it happened. Only when investigators are able to determine why an event or failure
occurred will they be able to specify workable
corrective measures that prevent future events of
the type observed.
Understanding why an event occurred is the
key to developing effective recommendations.
Imagine an occurrence during which an operator is instructed to close valve A; instead, the
operator closes valve B. The typical investigation would probably conclude operator error
was the cause.
This is an accurate description of what happened and how it happened. However, if the analysts stop here, they have not probed deeply
enough to understand the reasons for the mistake.
Therefore, they do not know what to do to prevent it from occurring again.
In the case of the operator who turned the
wrong valve, we are likely to see recommendations such as retrain the operator on the procedure, remind all operators to be alert when
QUALITY PROGRESS
I JULY 2004 I 45
QUALITY BASICS
manipulating valves or emphasize to all personnel
that careful attention to the job should be maintained at all times. Such recommendations do little
to prevent future occurrences.
Generally, mistakes do not just happen but can
be traced to some well-defined causes. In the case
of the valve error, we might ask, “Was the procedure confusing? Were the valves clearly labeled?
Was the operator familiar with this particular
task?”
The answers to these and other questions will
help determine why the error took place and
what the organization can do to prevent recur-
Identifying “severe weather”
as the root cause of parts not
being delivered on time to
customers is not appropriate.
rence. In the case of the valve error, example
recommendations might include revising the
procedure or performing procedure validation to
ensure references to valves match the valve labels
found in the field.
Identifying root causes is the key to preventing
similar recurrences. An added benefit of an effective
RCA is that, over time, the root causes identified
across the population of occurrences can be used to
target major opportunities for improvement.
If, for example, a significant number of analyses
point to procurement inadequacies, then resources
can be focused on improvement of this management
system. Trending of root causes allows development
of systematic improvements and assessment of the
impact of corrective programs.
Definition
Although there is substantial debate on the definition of root cause, we use the following:
1. Root causes are specific underlying causes.
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2. Root causes are those that can reasonably be
identified.
3. Root causes are those management has control
to fix.
4. Root causes are those for which effective recommendations for preventing recurrences can
be generated.
Root causes are underlying causes. The investigator’s goal should be to identify specific underlying causes. The more specific the investigator can
be about why an event occurred, the easier it will
be to arrive at recommendations that will prevent
recurrence.
Root causes are those that can reasonably be
identified. Occurrence investigations must be cost
beneficial. It is not practical to keep valuable manpower occupied indefinitely searching for the root
causes of occurrences. Structured RCA helps analysts get the most out of the time they have invested in the investigation.
Root causes are those over which management
has control. Analysts should avoid using general
cause classifications such as operator error, equipment failure or external factor. Such causes are not
specific enough to allow management to make
effective changes. Management needs to know
exactly why a failure occurred before action can be
taken to prevent recurrence.
We must also identify a root cause that management can influence. Identifying “severe weather”
as the root cause of parts not being delivered on
time to customers is not appropriate. Severe weather is not controlled by management.
Root causes are those for which effective recommendations can be generated. Recommendations
should directly address the root causes identified
during the investigation. If the analysts arrive at
vague recommendations such as, “Improve adherence to written policies and procedures,” then
they probably have not found a basic and specific
enough cause and need to expend more effort in the
analysis process.
Four Major Steps
The RCA is a four-step process involving the following:
1. Data collection.
2. Causal factor charting.
Causal Factor Chart
FIGURE 1
Burner
Part one
Electric
burner
shorts out
CF
Pan
Arcing heats
bottom of
aluminum
pan
Had it
not been
originally charged?
Fire
extinguisher
Pan
Jane
Had it
leaked?
Aluminum
melts,
forming
hole in pan
Fire extinguisher,
floor
Jane comes
to the door
Conclusion
Jane, Mary
How
much oil is
used? How
much chicken?
Chicken,
pan, oil Mary
Mary
begins
frying
chicken
5:00 pm
Pan
Mary
uses an
aluminum
pan
Grease ignites
when it
contacts
burner
What
exactly
did she see?
Had it
been
previously used?
Mary
Inspection tag
Assumed
Fire
generates
smoke
Jane rings
the doorbell
Mary
Mary
Mary sees
the fire
on the stove
Fire extinguisher
is not
charged
Mary
Mary
Mary leaves
the frying
chicken
unattended
CF
Fire starts
on the
stove
Mary
Mary meets
with Jane
Jane, Mary
Smoke
detector
alarms
Mary
Mary runs
into the
kitchen
Mary
Mary
Mary tries
to use
the fire
extinguisher
About 5:10 pm
Fire extinguisher
does not
operate when
Mary tries to use it
CF
Mary
10 minutes
Mary pulls
the plug
on the fire
extinguisher
Is "plug"
the same
as pin?
Does Mary
know how
to use a fire
extinguisher?
Mary
Mary
CF = Causal factor
Figure 1 continued on next page
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QUALITY BASICS
Part two
Did she know
this was wrong?
Lack of practice
fighting fires?
Did she do
anything else?
What is
Jane doing during
this time?
Mary, Jane
Mary
Mary, pan
Mary
Was Mary
trying to do this?
How long
did it take for the
FD to arrive?
Fire was a
grease fire
FD
dispatcher
Mary
Mary
Mary throws
water on
the fire
Mary, FD
Kitchen, Mary
Fire spreads
throughout
the kitchen
CF
Mary calls the
fire department
Time?
3. Root cause identification.
4. Recommendation generation and implementation.
Step one—data collection. The first step in the
analysis is to gather data. Without complete information and an understanding of the event, the
causal factors and root causes associated with the
event cannot be identified. The majority of time
spent analyzing an event is spent in gathering
data.
Step two—Causal factor charting. Causal factor
charting provides a structure for investigators to organize and analyze the information gathered during
the investigation and identify gaps and deficiencies
in knowledge as the investigation progresses. The
causal factor chart is simply a sequence diagram
with logic tests that describes the events leading up
to an occurrence, plus the conditions surrounding
these events (see Figure 1, p. 47).
Preparation of the causal factor chart should
begin as soon as investigators start to collect information about the occurrence. They begin with a
skeleton chart that is modified as more relevant
facts are uncovered. The causal factor chart should
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I JULY 2004 I www.asq.org
Did the FD
use the correct
techniques?
FD
Observation
FD, observation
Fire department
arrives
Fire department
puts out fire
Time?
Time?
Kitchen
destroyed
by fire
Other losses
from smoke and
water damage?
drive the data collection process by identifying
data needs.
Data collection continues until the investigators
are satisfied with the thoroughness of the chart
(and hence are satisfied with the thoroughness of
the investigation). When the entire occurrence has
been charted out, the investigators are in a good
position to identify the major contributors to the
incident, called causal factors. Causal factors are
those contributors (human errors and component
failures) that, if eliminated, would have either prevented the occurrence or reduced its severity.
In many traditional analyses, the most visible
causal factor is given all the attention. Rarely, however, is there just one causal factor; events are usually the result of a combination of contributors.
When only one obvious causal factor is addressed,
the list of recommendations will likely not be complete. Consequently, the occurrence may repeat
itself because the organization did not learn all that
it could from the event.
Step three—root cause identification. After all
the causal factors have been identified, the investigators begin root cause identification. This step
involves the use of a decision diagram called the
Root Cause Map (see Figure 2, p. 50) to identify the
underlying reason or reasons for each causal factor.
The map structures the reasoning process of the
investigators by helping them answer questions
about why particular causal factors exist or
occurred. The identification of root causes helps
the investigator determine the reasons the event
occurred so the problems surrounding the occurrence can be addressed.
Step four—recommendation generation and
implementation. The next step is the generation of
recommendations. Following identification of the
root causes for a particular causal factor, achievable
recommendations for preventing its recurrence are
then generated.
The root cause analyst is often not responsible
for the implementation of recommendations generated by the analysis. However, if the recommendations are not implemented, the effort expended in
performing the analysis is wasted. In addition, the
events that triggered the analysis should be expected to recur. Organizations need to ensure that recommendations are tracked to completion.
Presentation of Results
Root cause summary tables (see Table 1, p. 52)
can organize the information compiled during data
analysis, root cause identification and recommendation generation. Each column represents a major
aspect of the RCA process.
• In the first column, a general description of the
causal factor is presented along with sufficient
background information for the reader to be
able to understand the need to address this
causal factor.
• The second column shows the Path or Paths
through the Root Cause Map associated with
the causal factor.
• The third column presents recommendations
to address each of the root causes identified.
Use of this three-column format aids the investigator in ensuring root causes and recommendations are developed for each causal factor.
The end result of an RCA investigation is generally an investigation report. The format of the
report is usually well defined by the administrative
documents governing the particular reporting sys-
tem, but the completed causal factor chart and
causal factor summary tables provide most of the
information required by most reporting systems.
Example Problem
The following example is nontechnical, allowing
the reader to focus on the analysis process and not
the technical aspects of the situation. The following
narrative is the account of the event according to
Mary:
It was 5 p.m. I was frying chicken. My friend
Jane stopped by on her way home from the doctor, and she was very upset. I invited her into
the living room so we could talk. After about 10
minutes, the smoke detector near the kitchen
came on. I ran into the kitchen and found a fire
on the stove. I reached for the fire extinguisher
and pulled the plug. Nothing happened. The
fire extinguisher was not charged. In desperation, I threw water on the fire. The fire spread
throughout the kitchen. I called the fire department, but the kitchen was destroyed. The fire
department arrived in time to save the rest of
the house.
Data gathering began as soon as possible after
the event to prevent loss or alteration of the data.
The RCA team toured the area as soon as the fire
In many traditional analyses,
the most visible causal factor
is given all the attention.
department declared it safe. Because data from
people are the most fragile, Mary, Jane and the firefighters were interviewed immediately after the
fire. Photographs were taken to record physical
and position data.
The analysts then developed the causal factor
chart (see Figure 1, p. 47) to clearly define the
sequence of events that led to the fire. The causal
factor chart begins with the event; Mary begins frying chicken at 5 p.m. As the chart develops from
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QUALITY BASICS
FIGURE 2
Root Cause Map
Start here with each causal factor.
Section one
1
1
Equipment difficulty
Equipment
design problem
2
Equipment
reliability program
problem
6
5
Installation/
fabrication
Equipment
misuse
7
8
2
Design input/
output
15
Design input
LTA 16
Design output
LTA 17
Equipment
records
Equipment reliability
program design
less than adequate (LTA) 21
18
Equipment
design records
LTA 19
Equipment
operating/
maintenance
history LTA 20
No program 22
Program LTA 23
• Analysis/design
procedure LTA 24
• Inappropriate type
of maintenance
assigned 25
• Risk acceptance
criteria LTA 26
• Allocation of
resources LTA 27
Note: Node numbers correspond to matching page in Appendix A of the
Root Cause Analysis Handbook.
Standards,
policies or
administrative
controls (SPACs)
LTA 57
• No SPACs 59
• Not strict
enough 60
• Confusing,
contradictory or
incomplete 61
• Technical error 62
• Responsibility
for item/activity
not adequately
defined 63
• Planning, scheduling
or tracking of work
activities LTA 64
• Rewards/incentives
LTA 65
• Employee screening/
hiring LTA 66
Safety/hazard/
risk review 72
• Review LTA or
not performed 74
• Recommendations not
yet implemented 75
• Risk acceptance
criteria LTA 76
• Review procedure
LTA 77
SPACs not used 67
• Communication of
SPACs LTA 69
• Recently changed
• Enforcement LTA
70
71
Equipment reliability
program implementation
LTA
28
Corrective maintenance
LTA 29
• Troubleshooting/corrective
action LTA 30
• Repair implementation
LTA 31
Preventive maintenance
LTA 32
• Frequency LTA 33
• Scope LTA 34
• Activity implementation
LTA 35
Predictive maintenance
LTA 36
• Detection LTA 37
• Monitoring LTA 38
• Troubleshooting/
corrective action LTA 39
• Activity implementation
LTA 40
Product/material
control 85
• Handling LTA 87
• Storage LTA 88
• Packaging/
shipping LTA 89
• Unauthorized material
substitution 90
• Product acceptance
criteria LTA 91
• Product inspections
LTA 92
Not used 112
• Not available or
inconvenient to
obtain 113
• Procedure difficult
to use 114
• Use not required
but should be 115
• No procedure for
task 116
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Procedures
111
Proactive maintenance
LTA 41
• Event specification
LTA 42
• Monitoring LTA 43
• Scope LTA 44
• Activity implementation
LTA 45
Failure finding maintenance
LTA 46
• Frequency LTA 47
• Scope LTA 48
• Troubleshooting/
corrective action LTA 49
• Repair implementation 50
Routine equipment
rounds LTA 51
• Frequency LTA 52
• Scope LTA 53
• Activity implementation
LTA 54
Procurement
control 93
• Purchasing
specifications LTA 95
• Control of changes
to procurement
specifications LTA 96
• Material acceptance
requirements LTA 97
• Material inspections
LTA 98
• Contractor selection
LTA 99
Problem
identification
control 78
• Problem reporting
LTA 80
• Problem analysis
LTA 81
• Audits LTA 82
• Corrective action
LTA 83
• Corrective actions not
yet implemented 84
Administrative/
management
systems 55
Document and
configuration
control 100
• Change not
identified 102
• Verification of design/
field changes LTA
(no PSSR*) 103
• Documentation
content not kept
up to date 104
• Control of official
documents LTA 105
Misleading/confusing 117
• Format confusing or
LTA 118
• More than one action
per step 120
• No checkoff space
provided but should be 121
• Inadequate checklist 122
• Graphics LTA 123
• Ambiguous or confusing
instructions/
requirements 124
• Data/computations
wrong/incomplete 125
• Insufficient or excessive
references 126
• Identification of revised
steps LTA 127
• Level of detail LTA 128
• Difficult to identify 129
Customer
interface/
services 106
• Customer
requirements
not identified 108
• Customer needs
not addressed 109
• Implementation
LTA 110
Wrong/incomplete 130
• Typographical error 131
• Sequence wrong 132
• Facts wrong/
requirements not
correct 133
• Wrong revision or
expired procedure
revision used 134
• Inconsistency
between
requirements 135
• Incomplete/situation
not covered 136
• Overlap or gaps
between
procedures 137
Figure 2 continued on next page
Start here with each causal factor.
Section Two
1
1
Personal difficulty
Company
employee
9
Other difficulty
3
Contract
employee
Natural
phenomena
10
4
Sabotage/
horseplay
11
12
External
events
Other
13
14
2
Human factors
engineering
138
No training 164
• Decision not
to train 165
• Training
requirements not
identified 166
Immediate
supervision
Training
163
Training records
system LTA 167
• Training records
incorrect 168
• Training records
not up to date 169
No communication or
not timely 194
• Method unavailable or
LTA 195
• Communication between
work groups LTA 196
• Communication between
shifts and management
LTA 197
• Communication with
contractors LTA 198
• Communication with
customers LTA 199
180
Training LTA 170
• Job/task analysis
LTA 171
• Program design/
objectives LTA 172
• Lesson content
LTA 174
• On-the-job
training LTA 175
• Qualification
testing LTA 176
• Continuing
training LTA 177
• Training
resources LTA 178
• Abnormal events/
emergency
training LTA 179
Misunderstood
communication 200
• Standard
terminology not
used 201
• Verification/
repeat back not
used 202
• Long message 203
Wrong
instructions
204
Communications
192
Personal
performance
208
Preparation 181
• No preparation 182
• Job plan LTA 183
• Instructions to workers
LTA 184
• Walkthrough LTA 185
• Scheduling LTA 186
• Worker selection/
assignment LTA 187
Supervision during
work 188
• Supervision LTA 189
• Improper performance
not corrected 190
• Teamwork LTA 191
Problem
detection LTA 209
*Sensory/perceptual
capabilities LTA 210
*Reasoning
capabilities LTA 211
*Motor/physical
capabilities LTA 212
*Attitude/attention
LTA 213
*Rest/sleep LTA
(fatigue) 214
*Personal/medication
problems 215
Job turnover LTA 205
• Communication
within shifts LTA 206
• Communication
between shifts
LTA 207
*PSSR = Project scope summary report
Shape
Description
Primary difficulty source
Problem category
Workplace layout 140
• Controls/displays
LTA 141
• Control/display
integration/
arrangement LTA 143
• Location of
controls/displays
LTA 144
• Conflicting layouts 145
• Equipment
location LTA 146
• Labeling of
equipment or
locations LTA 147
Work environment 148
• Housekeeping LTA 149
• Tools LTA 150
• Protective clothing/
equipment LTA 151
• Ambient
conditions LTA 152
• Other environmental
stresses excessive 154
Workload 155
• Excessive control
action
requirements 156
• Unrealistic
monitoring
requirements 157
• Knowledge based
decision
required 158
• Excessive
calculation or
data manipulation
required 159
Intolerant
system 160
• Errors not
detectable 161
• Errors not
correctable 162
Root cause category
Near root cause
Root cause
© 1995, 1997, 1999, 2000 and 2001, ABSG Consulting Inc.
*Note: These nodes are for descriptive
purposes only.
QUALITY PROGRESS
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QUALITY BASICS
TABLE 1
Root Cause Summary Table
Event description: Kitchen is destroyed by fire and damaged by smoke and water.
Causal factor # 1
Description:
Mary leaves the frying chicken unattended.
Paths Through Root Cause Map
• Personnel difficulty.
• Administrative/management systems.
• Standards, policies or administrative
controls (SPACs) less than adequate (LTA).
• No SPACs.
Causal factor # 2
Description:
Electric burner element fails (shorts out).
Paths Through Root Cause Map
•
•
•
•
Causal factor # 3
Description:
Fire extinguisher does not operate when
Mary tries to use it.
Paths Through Root Cause Map
Paths Through Root Cause Map is a trademark of ABSG Consulting.
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Recommendations
• Implement a policy that hot oil is never left
unattended on the stove.
• Determine whether policies should be
developed for other types of hazards in the
facility to ensure they are not left unattended.
• Modify the risk assessment process or
procedure development process to address
requirements for personnel attendance
during process operations.
Recommendations
• Replace all burners on stove.
• Develop a preventive maintenance strategy
to periodically replace the burner elements.
• Consider alternative methods for preparing
chicken that may involve fewer hazards,
such as baking the chicken or purchasing
the finished product from a supplier.
Recommendations
•
•
•
•
Equipment difficulty.
Equipment reliability program problem.
Equipment proactive maintenance LTA.
Activity implementation LTA.
• Refill the fire extinguisher.
• Inspect other fire extinguishers in the
facility to ensure they are full.
• Have incident reports describing the use of
fire protection equipment routed to
maintenance to trigger refilling of the fire
extinguishers.
•
•
•
•
Equipment difficulty.
Equipment reliability program problem.
Administrative/management systems.
Problem identification and control LTA.
• Add this fire extinguisher to the audit list.
• Verify that all fire extinguishers are on the
quarterly fire extinguisher audit list.
• Have all maintenance work requests that
involve fire protection equipment routed to
the safety engineer so the quarterly
checklists can be modified as required.
Causal factor # 4
Description:
Mary throws water on fire.
Equipment difficulty.
Equipment reliability program problem.
Equipment reliability program design LTA.
No program.
Event #: 2003-1
Paths Through Root Cause Map
•
•
•
•
•
Personnel difficulty.
Company employee.
Training.
Training LTA.
Abnormal events/emergency training LTA.
Recommendations
• Provide practical (hands-on) training
on the use of fire extinguishers. Classroom
training may be insufficient to adequately
learn this skill.
• Review other skill based activities to
ensure appropriate level of hands-on training
is provided.
• Review the training development process
to ensure adequate guidance is provided for
determining the proper training setting (for
example,classroom, lab, simulator, on the job
training, computer based training).
left to right, the sequences begin to unfold. The loss
events—kitchen destroyed by fire and other losses
from smoke and water damage—are the shaded
rectangles in the causal factor chart.
Although we read the chart from left to right, it
is developed from right to left (backwards).
Development always starts at the end because that
is always a known fact. Logic and time tests are
used to build the chart back to the beginning of
the event. Numerous questions are usually generated that identify additional necessary data.
After the causal factor chart was complete (additional data were gathered to answer the questions
shown in Figure 1), the analysts identified the factors that influenced the course of events. There are
four causal factors for this event (see Table 1).
Elimination of these causal factors would have
either prevented the occurrence or reduced its severity. Note the recommendations in Table 1 are written
as if Mary’s house were an industrial facility.
Notice that causal factor two may be unexpected. It wasn’t overheating of the oil or splattering of
the oil that ignited the fire. If the wrong causal factor is identified, the wrong corrective actions will
be developed.
The application of the technique identified that
the electric burner element failed by shorting out.
The short melted Mary’s aluminum pan, releasing
the oil onto the hot burner, starting the fire.
The analyst must be willing to probe the data
first to determine what happened during the occurrence, second to describe how it happened, and
third to understand why.
Root Cause Analysis Handbook, WSRC-IM-91-3, Department of
Energy, 1991 (and earlier versions).
Root Cause Analysis Handbook: A Guide to Effective
Investigation, ABSG Consulting Inc., 1999.
User’s Guide for Reactor Incident Root Cause Coding Tree, revision five, DPST-87-209, E.I. duPont de Nemours, Savannah River Laboratory, 1986.
JAMES J. ROONEY is a senior risk and reliability engineer
with ABSG Consulting Inc.’s Risk Consulting Division in
Knoxville, TN. He earned a master’s degree in nuclear engineering from the University of Tennessee. Rooney is a Fellow
of ASQ and an ASQ certified quality auditor, quality auditor-hazard analysis and critical control points, quality engineer, quality improvement associate, quality manager and
reliability engineer.
LEE N. VANDEN HEUVEL is a senior risk and reliability
engineer with ABSG Consulting Inc.’s Risk Consulting
Division in Knoxville, TN. He earned a master’s degree in
nuclear engineering from the University of Wisconsin.
Vanden Heuvel co-authored the Root Cause Analysis
Handbook: A Guide to Effective Incident Investigation, co-developed the RootCause Leader software and was
a co-author of the Center for Chemical Process Safety’s
Guidelines for Investigating Chemical Process
Incidents. He develops and teaches courses on the subject.
BIBLIOGRAPHY
Accident/Incident Investigation Manual, second edition,
DOE/SSDC 76-45/27, Department of Energy.
Events and Causal Factors Charting, DOE/SSDC 76-45/14,
Department of Energy, 1985.
Ferry, Ted S., Modern Accident Investigation and Analysis, second edition, John Wiley and Sons, 1988.
Guidelines for Investigating Chemical Process Incidents,
American Institute of Chemical Engineers, Center for
Chemical Process Safety, 1992.
Occupational Safety and Health Administration Accident
Investigation Course, Office of Training and Education, 1993.
Please
comment
If you would like to comment on this article,
please post your remarks on the Quality Progress
Discussion Board at www.asq.org, or e-mail them
to editor@asq.org.
QUALITY PROGRESS
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