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Root Cause Analysis; Definition, Principles & Methods

What Is Root Cause Analysis?

Root cause analysis abbreviated as (RCA) is the process of discovering the root causes of problems in order to identify appropriate solutions for the problem. Root cause analysis makes use of principles, techniques, and methodologies to identify the root causes of an event or trend and show where processes or systems failed. 


When Do We Need RCA

Examples of events where RCA is used to solve problems and provide preventive actions include:

  • Major accidents
  • Everyday incidents
  • Minor near-misses
  • Human errors
  • Maintenance problems
  • Medical mistakes
  • Productivity issues
  • Manufacturing mistakes
  • Environmental releases
  • Risk analysis, risk mapping


Core Objectives Of RCA

  1. To discover the root cause of a problem or event.
  2. To fully understand how to fix, compensate, or learn from any underlying issues within the root cause.
  3. To apply the result of the analysis to systematically prevent future issues or to repeat successes.
  4. To also modify core process and system issues in a way that prevents future problems.


Goals & Benefits Of RCA


The primary goal of using RCA is to analyze problems or events to identify:

  • What happened
  • How it happened
  • Why it happened
  • Actions for preventing reoccurrence are developed


Implementing RCA will help the agency:

  • Identify barriers and the causes of problems, so that permanent solutions can be found.
  • Develop a logical approach to problem-solving, using data that already exists in the agency.
  • Identify current and future needs for organizational improvement.
  • Establish repeatable, step-by-step processes, in which one process can confirm the results of another.


Core Principles For Conducting A Successful Root Cause Analysis

There are a few core principles that guide effective root cause analysis which will help the analysis quality, and also help the analyst gain trust and buy-in from stakeholders, clients, or patients.

  • Focus on correcting and remedying root causes rather than just symptoms.
  • Do not ignore the importance of treating symptoms for short term relief.
  • Realize there can be, and often are, multiple root causes.
  • Focus on HOW and WHY something happened, not WHO was responsible.
  • Be methodical and find concrete cause-effect evidence to back up root cause claims.
  • Provide enough information to inform a corrective course of action.
  • Consider how a root cause can be prevented in the future.


RCA Steps

Despite the different approaches among the various schools of root cause analysis and the specifics of each application domain, RCA generally follows the same four steps:

  1. Identification and description: Effective problem statements and event descriptions (as failures, for example) are helpful and usually required to ensure the execution of appropriate root cause analyses.
  2. Chronology: RCA should establish a sequence of events or timeline for understanding the relationships between contributory (causal) factors, the root cause, and the problem under investigation.
  3. Differentiation: By correlating this sequence of events with the nature, the magnitude, the location, and the timing of the problem, and possibly also with a library of previously analyzed problems, RCA should enable the investigator(s) to distinguish between the root cause, causal factors, and non-causal factors. One way to trace down root causes consists in using hierarchical clustering and data-mining solutions (such as graph-theory-based data mining). Another consists in comparing the situation under investigation with past situations stored in case libraries, using case-based reasoning
  4. Causal graphing: Finally, the investigator should be able to extract from the sequences of events a subsequence of key events that explain the problem, and convert it into a causal graph.


To be effective, root cause analysis must be performed systematically. A team effort is typically required. For aircraft accident analyses, for example, the conclusions of the investigation and the root causes that are identified must be backed up by documented evidence.


Read Also: 6 Methods of risk assessment you should know

Root Cause Analysis Techniques And Methods

RCA can be comfortably be broken down into four steps:

  • Identify and describe the problem clearly.
  • Establish a timeline from the normal situation up to the time the problem occurred.
  • Distinguish between the root cause and other causal factors (e.g., using event correlation).
  • Establish a causal graph between the root cause and the problem.

RCA generally serves as input to a remediation process. The name of this process varies from one application domain to another. According to ISO/IEC 31010, RCA may include the techniques:

  • 5 Whys
  • Failure mode and effects analysis (FMEA),
  • Fault tree analysis,
  • Ishikawa diagram,
  • Pareto analysis, etc.


5 Whys

Here is how the 5 WHY’S approach work – For every answer to a WHY question, follow it up with an additional, deeper “Ok, but WHY?” question. Common wisdom suggests that about five WHY questions can lead us to most root causes—but we could need as few as two or as many as 50 WHYs.

Example: Let’s think back to our football concussion example. First, our player will present a problem: Why do I have such a bad headache? This is our first WHY. First answer: Because I can’t see straight. Second why: Why can’t you see straight? Second answer: Because I my head hit the ground. Third why: Why did your head hit the ground? Third answer: I got hit tackled to the ground and hit my head hard. Fourth why: Why did hitting the ground hurt so much? Fourth answer: Because I wasn’t wearing a helmet. Fifth why: Why weren’t you wearing a helmet? Fifth answer: Because we didn’t have enough helmets in our locker room.

After these five questions, we discover that the root cause of the concussion was most likely from a lack of available helmets. In the future, we could reduce the risk of this type of concussion by making sure every football player has a helmet.


Failure Mode and Effect Analysis (FMEA)

FMEA Analysis (Failure Mode and Effects Analysis) is a failure analysis method which works by discovering potential failures that may exist within the design of a product or process.

FMEA Analysis (Failure Mode and Effects Analysis) can be fragmented into two-part:

  1. Failure mode: Failure modes are the ways in which a process can fail.
  2. Effect: Effects are the ways that these failures can lead to waste, defects or harmful outcomes. It can be said to be negative consequence associated with the failure.

FMEA aim at allowing organizations to anticipate failure during the design stage by identifying all of the possible failures in a design or manufacturing process.


Fault Tree Analysis

A fault tree analysis is a top-down map used to identify the causes of an identified hazard or an undesirable event. This could be anything from your car being stolen to a jet crash. This method was originally used in aerospace but it’s become a tool that can be used to analyze hazards in any workplace.

The way the analysis works is by drawing out a kind of map. At the very top should be the undesired event itself, something like “Jet loses power.”

Under that event, you would list all possible components and systems that could have caused that event to happen. Each of them is marked by an icon that either indicates “And” or “Or.” An “Or” cause is a single item that could, by itself, cause the event. An “And” indicates that the cause would only be one of the factors that contributed to the undesirable event.

So, if we take our example of the jet losing power, the “Or” items could include:


  • Bird ingestion by the engine
  • Internal engine failures
  • Pneumatic bleed malfunctions
  • Internal clearance changes

Once you’ve identified all of the potential causes that could lead to the negative event, you can proceed to set up control measures for them. That’s what makes the fault tree analysis such a helpful tool: you don’t have to wait to identify the hazard that led to the incident you want to prevent. Instead, it lets you take proactive steps to deal with any of the hazards that could lead to it.


Read AlsoHow to use the risk assessment matrix effectively

Ishikawa Diagram

Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams, or Fishikawa) are causal diagrams created by Kaoru Ishikawa that show the potential causes of a specific event.

Common uses of the Ishikawa diagram are product design and quality defect prevention to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation. Causes are usually grouped into major categories to identify and classify these sources of variation.


In the Ishikawa diagram, the defect is shown as the fish’s head, facing to the right, with the causes extending to the left as fishbones; the ribs branch off the backbone for major causes, with sub-branches for root-causes, to as many levels as required.


The steps to depicting cause and effect on a Fishbone diagram are-

  1. Define your problem
  2. Brainstorm with the team on possible causes for the problem
  3. Use the 6 Ms while doing so
    • Man – people performing the process or involved
    • Machine – equipment and tools used within the process
    • Method – procedures followed
    • Material – Inputs required within the process
    • Measurement – data on input or product specifications
    • Mother nature – environment in which men and machines operate
  4. Categorise all the causes as per the 6Ms
  5. Prioritise basis data and team view. In the above diagram, the team believes the highlighted causes are the major contributory factors.
  6. Brainstorm solutions for the prioritised causes and implement


Pareto Analysis

Pareto Analysis uses the Pareto Principle – also known as the “80/20 Rule” – which was coined by Italian economist, Vilfredo Pareto, in his 1896 book, “Cours d’économie politique.”


The Pareto Principle states that 80 percent of a project’s benefit comes from 20 percent of the work. Or, conversely, that 80 percent of problems can be traced back to 20 percent of causes. Pareto Analysis identifies the problem areas or tasks that will have the biggest payoff. The tool has several benefits, including:

  • Identifying and prioritizing problems and tasks.
  • Helping people to organize their workloads more effectively.
  • Improving productivity.
  • Improving profitability.

Steps to conduct a Pareto analysis are –

  • Define categories or classifications for the causes
  • Collect data from historical sources or collect data through logs
  • Assign a time period for which the data pertains to or to be collected
  • Calculate the number of occurrences or observations for each of the categories
  • Convert the numbers into percentage of total
  • Sort the data by numbers, largest to smallest
  • Compute cumulative percentages
  • Draw a graph using Minitab or Microsoft Excel
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