Root cause analysis

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Root cause analysis (RCA) is a class of problem solving methods aimed at identifying the root causes of problems or events. The practice of RCA is predicated on the belief that problems are best solved by attempting to correct or eliminate root causes, as opposed to merely addressing the immediately obvious symptoms. By directing corrective measures at root causes, it is hoped that the likelihood of problem recurrence will be minimized. However, it is recognized that complete prevention of recurrence by a single intervention is not always possible. Thus, RCA is often considered to be an iterative process, and is frequently viewed as a tool of continuous improvement.

RCA, initially is a reactive method of problem detection and solving. This means that the analysis is done after an event has occurred. By gaining expertise in RCA it becomes a pro-active method. This means that RCA is able to forecast the possibility of an event even before it could occur.

Root cause analysis is not a single, sharply defined methodology; there are many different tools, processes, and philosophies of RCA in existence. However, most of these can be classed into five, very-broadly defined "schools" that are named here by their basic fields of origin: safety-based, production-based, process-based, failure-based, and systems-based.

• Safety-based RCA descends from the fields of accident analysis and occupational safety and health.
• Production-based RCA has its origins in the field of quality control for industrial manufacturing.
• Process-based RCA is basically a follow-on to production-based RCA, but with a scope that has been expanded to include business processes.
• Failure-based RCA is rooted in the practice of failure analysis as employed in engineering and maintenance.
• Systems-based RCA has emerged as an amalgamation of the preceding schools, along with ideas taken from fields such as change management, risk management, and systems analysis.

Despite the seeming disparity in purpose and definition among the various schools of root cause analysis, there are some general principles that could be considered as universal. Similarly, it is possible to define a general process for performing RCA.

General principles of root cause analysis

1. Aiming performance improvement measures at root causes is more effective than merely treating the symptoms of a problem.
2. To be effective, RCA must be performed systematically, with conclusions and causes backed up by documented evidence.
3. There is usually more than one potential root cause for any given problem.
4. To be effective the analysis must establish all known causal relationships between the root cause(s) and the defined problem.
5. Root cause analysis transforms an old culture that reacts to problems to a new culture that solves problems before they escalate, creating a variability reduction and risk avoidance mindset.

General process for performing and documenting an RCA-based Corrective Action

Notice that RCA (in steps 3, 4 and 5) forms the most critical part of successful corrective action, because it directs the corrective action at the root of the problem. That is to say, it is effective solutions we seek, not root causes. Root causes are secondary to the goal of prevention, and are only revealed after we decide which solutions to implement.

1. Define the problem.
2. Gather data/evidence.
3. Ask why and identify the causal relationships associated with the defined problem.
4. Identify which causes if removed or changed will prevent recurrence.
5. Identify effective solutions that prevent recurrence, are within your control, meet your goals and objectives and do not cause other problems.
6. Implement the recommendations.
7. Observe the recommended solutions to ensure effectiveness.
8. Variability Reduction methodology for problem solving and problem avoidance.

Root cause analysis techniques

• Barrier analysis - a technique often used in particularly in process industries. It is based on tracing energy flows, with a focus on barriers to those flows, to identify how and why the barriers did not prevent the energy flows from causing harm.
• Bayesian inference
• Causal factor tree analysis - a technique based on displaying causal factors in a tree-structure such that cause-effect dependencies are clearly identified.
• Change analysis - an investigation technique often used for problems or accidents. It is based on comparing a situation that does not exhibit the problem to one that does, in order to identify the changes or differences that might explain why the problem occurred.
• Current Reality Tree A method developed by Eliahu M. Goldratt in his Theory of Constraints that guides an investigator to identify and relate all root causes using a cause-effect tree whose elements are bound by rules of logic (Categories of Legitimate Reservation). The CRT begins with a brief list of the undesirables things we see around us, and then guides us towards one or more root causes. This method is particularly powerful when the system is complex, there is no obvious link between the observed undesirable things, and a deep understanding of the root cause(s) is desired.
• Failure mode and effects analysis Also known as FMEA.
• Fault tree analysis
• 5 Whys
• Ishikawa diagram, also known as the fishbone diagram or cause and effect diagram. The Ishikawa diagram is the preferred method for Project Managers for conducting RCA, mainly due to its simplicity, and the complexity of the rest of the methods^[1].
• Kepner-Tregoe Problem Analysis - a root cause analysis process developed in 1958, which provides a fact-based approach to systematically rule out possible causes and identify the true cause
• Pareto analysis
• RPR Problem Diagnosis - An ITIL-aligned method for diagnosing IT problems.

Common cause analysis (CCA) common modes analysis (CMA) are evolving engineering techniques for complex technical systems to determine if common root causes in hardware, software or highly integrated systems interaction may contribute to human error or improper operation of a system. Systems are analyzed for root causes and causal factors to determine probability of failure modes, fault modes, or common mode software faults due to escaped requirements. Also ensuring complete testing and verification are methods used for ensuring complex systems are designed with no common causes that cause severe hazards. Common cause analysis are sometimes required as part of the safety engineering tasks for theme parks, commercial/military aircraft, spacecraft, complex control systems, large electrical utility grids, nuclear power plants, automated industrial controls, medical devices or other safety safety-critical systems with complex functionality.

Basic elements of root cause

• Materials
  • Defective raw material
  • Wrong type for job
  • Lack of raw material
• Machine / Equipment
  • Incorrect tool selection
  • Poor maintenance or design
  • Poor equipment or tool placement
  • Defective equipment or tool
• Environment
  • Orderly workplace
  • Job design or layout of work
  • Surfaces poorly maintained
  • Physical demands of the task
  • Forces of nature
• Management
  • No or poor management involvement
  • Inattention to task
  • Task hazards not guarded properly
  • Other (horseplay, inattention....)
  • Stress demands
  • Lack of Process
• Methods
  • No or poor procedures
  • Practices are not the same as written procedures
  • Poor communication
• Management system
  • Training or education lacking
  • Poor employee involvement
  • Poor recognition of hazard
  • Previously identified hazards were not eliminated

See also

• Failure mode and effects analysis
• Fault tree analysis
• Forensic engineering
• Fix it twice

References