Bringing the 5-Why’s, Fishbone and Event & Causal Factors Chart Into the 21st Century!

11 minute read


BlueDragon Hyper-Integrated Causal Analysis (HCA) was created in the commercial nuclear industry and is rapidly becoming the root cause analysis (RCA) method of choice in the Energy sector. HCA is by far the most advanced and comprehensive problem solving methodology available. It can be used to solve any level of human-centric problems and it can be applied in any industry.

After researching other industries such as Aeronautics and Space (CFR Title 14), Food and Drug (CFR Title 21) and Public Health (Title 42), it would appear that those industries are lagging behind the commercial nuclear industry in their RCA methodologies. A majority of these industries still use traditional (and antiquated) tools such as the Fishbone, the 5-Whys and Event and Causal Factors (E&CF) charts in their RCA tool kit. Published articles from these industries reflect the need to expand beyond the 5-Whys and the Fishbone, but have not offered clear alternatives or recommendations for next-generation methodologies.

In this blog, we provide a clear option for updating the Fishbone, the 5-Whys and other tools and techniques with a modern, lean, agile and efficient problem-solving method that was built for today’ need for speed and accuracy.


There are good reasons why RCA methods in use at other industries are lagging behind commercial nuclear power. Over the course of its history, nuclear power plants have suffered serious incidents that threatened the entire industry. Indeed, some countries have dramatically shifted away from nuclear power because of these incidents (i.e. Germany, Spain). Some of the most significant incidents include:

  • Brown’s Ferry Fire (March 22, 1975)
  • Three Mile Island Core Meltdown (March 28, 1979)
  • Chernobyl (April 26, 1986)
  • Davis-Besse Reactor Vessel Head Degradation (February 16, 2002)
  • Fukushima Daiichi (March 11, 2011)

These and other significant incidents have resulted in additional, more stringent regulations that raised the bar for many programs and processes (including RCA), and greatly increased regulatory oversight. Unlike every nuclear power plant in the country, most industries do not have a Resident Inspector and a Senior Resident Inspector assigned 100% of the time to provide oversight onsite. After Three Mile Island, the nuclear power industry also created an independent pseudo-regulatory body called the Institute of Nuclear Power Operations (INPO), to evaluate performance at every power plant in the country every two years. The overall result has been rapid advancement in programs, processes and procedures.

In my own case, I became a RCA subject matter expert and practitioner in 1989, as part of the Florida Power & Light team that won the Deming Prize from the Japanese Union of Scientists and Engineers. For three decades I continued to learn and improve on the many traditional causal analysis tools and techniques taught in the industry. To create HCA, I combined the best features of many traditional tools and techniques into one scalable, lean and agile approach that identifies the deepest-seated causes of complex, human-centric problems with amazing speed and accuracy.

BlueDragon HCA has a lot to offer the Energy, Oil & Gas, Aerospace, Pharma, Healthcare, and all other regulated industries that require significant problems to be investigated, their causes identified, and actions taken to prevent recurrence. I’d like to illustrate by commenting on three traditional tools that are antiquated but are still widely used: the Fishbone, the 5-Whys and the Event & Causal Factors Chart.


The Fishbone:

The Fishbone was introduced in the 1940’s by Dr. Kaoru Ishikawa. I’m a big fan of his work, as Dr. Ishikawa put cause and effect analysis on the map in a very visual way. The bones in the Fishbone (i.e. man, method, machine, materials, environment) happen to strongly correlate with the main areas in the Anatomy of an Event (shown in the chart below), which we have studied in the nuclear power sector to make sure we cover all the bases when investigating issues. We take the approach that there are 100s of latent weaknesses in our organizations that are causing problems, and every incident or event is an opportunity to uncover and address as many of those latent weaknesses as we can. To do so, our methodology must use every bit of evidence we can gather and analyze, and then to explore relevant information in those key areas highlighted in the anatomy of an event (which we call themes).

However, the Fishbone should not be used for more than the simplest of issues, and certainly not for conducting RCA. The true value of the Fishbone is that it prompts us to evaluate a problem from different perspectives (the bones), providing for a more thorough investigation and a better overall understanding of the causes of the event.

I’ve also noted that the Fishbone is not taught and used properly in many cases. To be used properly, each branch that comes off the bones of the Fishbone should be treated much the same was a 5-Why staircase, but with no limitation on five (a misconception addressed later). Many organizations do not use the 5-Whys in combination with the Fishbone for maximum effectiveness. The result is a diagram like the one shown below that is difficult to interpret and unlikely to identify any root causes.

If you consider that each branch that comes off of one of the bones as an individual Line of Inquiry, it would only take about a dozen lines of inquiry to overwhelm the Fishbone and our ability to interpret the results. Here is the last Fishbone I ever did in 2007 (because I was instructed to use the method by a client). Note that even after incorporating the Why staircases and color-coding the common causes, I would still have to explain which ones are considered root causes and which ones are contributing factors.

The bones on a Fishbone are similar to the themes from the Anatomy of an Event. Watch this short video that explains how to convert the Fishbone into a more ergonomic chart that is user-friendly.

In the photograph below, the chart has over 100 Lines of Inquiry. Each Line of Inquiry is a Why staircase. Note that our Lines of Inquiry go way deeper than 5 questions, sometimes as much as 20 questions deep. If you attempt to draw this diagram on a Fishbone, it would not be a fun day. We color-code the common causes to make it a visually powerful storyboard and the results are clear; the root causes are going to be at the bottom, at the end of all of our cause-and-effect analysis. We can expand this diagram to accommodate as many Lines of Inquiry as we generate, based on the evidence and the complexity of the event. The Fishbone would become unwieldy after about a dozen Lines of Inquiry.

The 5-Whys:

The 5-Whys was originally developed in the 1930s by Sakichi Toyoda to understand why new product features or manufacturing techniques were needed, and was not developed for root cause analysis. The technique was later used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies. It became a critical component of problem-solving training, delivered as part of the induction into the Toyota Production System. The architect of the Toyota Production System, Taiichi Ohno, described the 5-Whys method as “the basis of Toyota’s scientific approach: by repeating why five times, the nature of the problem as well as its solution becomes clear.” The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing and Six Sigma.

There are a number of common misconceptions about the 5-Whys, and here are three of the biggest.

  1. “The 5-Whys is a root cause methodology.” Not true. Many organizations list the 5-Whys in their RCA tool kit as an approved RCA methodology and this, by far, is the biggest misconception out there. The 5-Whys is a method to capture “cause & effect analysis,” the basic building block for conducting an apparent cause or root cause analysis. But a credible RCA requires many more than one or a few 5-Whys because a single (or even a few) 5-Whys do not provide any assurance that we will identify the deepest-seated causes. Even if there is a chance that a single 5-Why staircase can identify a root cause, there would not be enough “demonstrable rigor” to provide the necessary confidence to ourselves, our managers and our regulators, that we actually identified the root causes. I have reviewed dozens of approved RCA reports that used a single or a couple of 5-Why staircases to complete the analysis, and they fall short of coming close to the deepest-seated causes. In sharp contrast, HCA generates between 30 and 100 5-Whys (we call them Lines of Inquiry) to complete a comprehensive RCA. The Lines of Inquiry are quickly identified when we place available information on the BlueDragon framework shown below.
  2. “We only have to go about 5 questions deep before getting to the root causes.” Not true. We continue to ask follow-up questions until there are no more answers. And if we went too far (i.e., way past the control of the organization, such as the Congressional Budget), we go back to the previous, actionable answer.
  3. “Repeatedly asking the question “WHY” is the most effective way to conduct cause and effect analysis.” Not True. Asking WHY is the most elementary way to conduct cause and effect analysis. BlueDragon HCA uses Socratic follow-up questions, a more sophisticated approach that helps us formulate questions that seek clarification, probe assumptions, probe the evidence and challenge points of view.

Event and Causal Factors Charts:

E&CF charts have also been used for decades and are an improvement over the 5-Whys because it includes a timeline, and pulls 5-Why staircases (cause and effect analysis) from the timeline. In effect, it greatly increased the number of 5-Why (lines of inquiry) that are used in the analysis. I used E&CF charts effectively, in combination with other tools and techniques, until 2012. The picture below is the last E&CF chart I developed for an incident at a Uranium processing facility.

The strength of the E&CF chart (i.e. the ability to initiate 5-Whys or lines of inquiry from the timeline) actually became its weakness. E&CF charts only initiate cause and effect analysis from the timeline, and we need to use other information to develop a better analysis. Information such as the administrative requirements and physical barriers that should have prevented the events (we call them the “defenses”), and the themes from the anatomy of an event to make sure we looked in all the right places.

I spent decades conducting RCAs, audits and assessments where I used the traditional tools and methods, but was frustrated that I had to use a number of separate tools like an E&CF chart and a Barrier Analysis table, which then had to be integrated into a single narrative. The traditional RCA methods were both antiquated and time consuming. We also took subject matter experts from their mission critical tasks for weeks at time, which no one likes to do. Some organizations actually down-classify their events to avoid doing a RCA, because they are so time consuming.

Over the years I modified the E&CF chart by keeping the timeline, but separating it from the cause & effect analysis. I added two more lines on the chart: the applicable barriers (the administrative requirements and physical/cyber barriers that should have prevented the event) so we could conduct a Barrier Analysis, and the themes from the Anatomy of an Event (the bones on the Fishbone). And that is how the BlueDragon HCA framework was originally developed. In the past five years we have continued to evolve and improve HCA by more clearly demonstrating our foundational concepts such as Socio-technical Systems Theory and High Reliability Organization principles.

The Hyper-Integrated Causal Analysis (HCA) Framework

Why do we call this RCA methodology “Hyper-Integrated”? Here are the tools and techniques that are now performed seamlessly using HCA.

  • Human Performance Evaluations
  • Comparative Timeline Analysis
  • Analysis of Defenses (Barrier Analysis)
  • Task/Change Analysis
  • Investigation of themes from the Anatomy of an Event (bones from the Fishbone)
  • Development of Lines of Inquiry
  • Socratic follow-up questioning
  • Cause and Effect Analysis
  • Common Cause Analysis
  • 5-Why Staircases and Cause Trees
  • Events & Causal Factors Charts

The basic components that make up an HCA chart are:

  • Timelines: the sequence of events. In HCA we split out various timelines that separate out how work was controlled, the human performance aspects of the events, timelines for important decisions in various programs, and also a timeline for the event response.
  • Defenses: here’s where we identify the administrative requirements (i.e. regulations, programs, procedures), physical and cyber barriers that are in place to prevent the issue we are investigating. We use this list to conduct an “Analysis of Defenses” in a seamless manner, to evaluate the effectiveness of these defenses by comparing what happened with what should have happened (previously called “Barrier Analysis”).
  • Themes: the five basic themes on our HCA chart come from the Anatomy of an Event, which correlate directly with the bones on the Fishbone. You can add additional themes as they emerge. These themes help us group our lines of inquiry into an organized approach for our cause and effect analysis.
  • Lines of Inquiry: these are the initial questions that we use to begin our cause & effect analysis. HCA has a very organized and disciplined approach to developing lines of inquiry, which ensures complete coverage of the problem and assures that we will identify the deepest-seated causes.

With timelines, defenses, themes and the lines of inquiry in front of us on one chart, we can analyze the information in an integrated manner, dramatically shortening the time it takes to complete the analysis.

With the BlueDragon HCA framework, RCAs that usually take weeks and months can be completed in hours and days, while ensuring better accuracy and more demonstrable rigor. Our average times to complete a moderately complex HCA is approximately 5 days. The value of the HCA methodology is reaffirmed by how rapidly HCA has been adopted by the nuclear weapons complex and the Department of Energy’s National Laboratories such as Savannah River, Sandia, Brookhaven, Los Alamos, Lawrence Livermore and other DOE Uranium processing sites. And in 2021, by the Westinghouse Nuclear Division.

RCA is a universal language and the HCA methodology can be readily implemented in any industry where it is important to conduct a rigorous RCA to identify the deepest-seated causes of problems, and take corrective actions and actions to prevent recurrence (also known as CAPA). These include Aerospace, Healthcare and Pharma, which seem to be lagging in their RCA methodologies.


Update your traditional tools such as the Fishbone, 5-Whys and E&CF charts, to the BlueDragon Hyper-Integrated Causal Analysis methodology, the next generation of RCA methodologies.

  1. Adopting the HCA Framework integrates the best features of traditional tools, such as the bones from the Fishbone, the timeline from Events and Causal Factors Charts, and the 5-Whys that form the basic building block of cause & effect analysis.
  2. HCA is agile and lean, allowing us to identify the deepest-seated causes of human-centric problems with amazing speed and accuracy. It does so by changing many paradigms that cost organizations time and resources and generate less effective results. For example, HCA uses small teams, and subject matter experts (SMEs) are only used as needed (for an hour or two), allowing them to stay on mission critical tasks. During the analysis, HCA can process over 100 SMEs in 1 week to participate in the analysis, working towards the final product from the start. The interview process is also dramatically different: it’s totally transparent and we do require taking copious notes that have to be reviewed and synthesized later – we work on the final chart from the start. The HCA interview process is also designed to eliminate bias from team members and from those being interviewed. And, the analytical process generates an accurate storyboard that demonstrates the level of rigor used in the investigation, clearly identifies the deepest-seated causes, and makes the results highly defendable.
  3. Using HCA Rapid and Comprehensive Investigations proactively is a great approach to managing risk. HCA Rapid Investigations can be used on lower level events in support of your trending and analysis programs. The results can be used to identify negative performance trends. Once a negative trend is identified, a more rigorous HCA Comprehensive Investigation can be completed, to identify the deepest-seated causes of the negative trends. By taking this proactive (pre-emptive) approach, we eliminate the root causes that are present and would eventually bypass our defenses to cause significant events. This proactive use of HCA is integral to Risk Management and a key to establishing a continuous improvement culture.

For more information on BlueDragon HCA, visit our website at: or contact us at:

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