Root Cause Analysis

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.

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

Aiming corrective measures at root causes is more effective than merely treating the symptoms of a problem.
To be effective, RCA must be performed systematically, and conclusions must be backed up by evidence.
There is usually more than one root cause for any given problem.

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.

Define the problem.
Gather data/evidence.
Identify issues that contributed to the problem.
Find root causes.
Develop solution recommendations.
Implement the recommendations.
Observe the recommended solutions to ensure effectiveness.

[edit] Root cause analysis techniques

5 Whys
Failure mode and effects analysis
Pareto analysis
Fault tree analysis
Bayesian inference
Ishikawa diagram, also known as the fishbone diagram or cause and effect diagram
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.
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.
Causal factor tree analysis - a technique based on displaying causal factors in a tree-structure such that cause-effect dependencies are clearly identified.

Basic Elements of Root Cause