Evaluating Root Cause Analysis Processes

What are the Most Common Root Cause Analysis Processes?

This page looks at the similarities and differences between five common techniques organizations use for root cause analysis – the 5 Whys, Kepner-Tregoe Problem Analysis, fishbone or Ishikawa diagrams, change analysis, fault tree analysis – and the TapRooT® root cause analysis process.

For help in evaluating root cause analysis processes, I discuss these techniques below. Then, I present a summary of the eight advantages the TapRooT® root cause analysis process provides. You get to decide which approach might work the best for you.

LISTEN to my ‘Root Cause Analysis FAQs’ Real Life Work podcast episode!

Evaluating Root Cause Analysis Options: 5 Whys

5 Why Features:

From my perspective, the Five Whys represent more of a conceptual, versus a systematic, fact-driven approach, to root cause analysis. It was adopted from the Japanese approach to management, and most notably practiced by Mr. Shigeo Shingo. Shingo would use the five whys on the production floor when he would tour manufacturing sites. In essence, Mr. Shingo would continue to ask why five or more times to get to the true cause of a problem. His questions were structured to help lead the employees he was talking to towards the problem’s source.

5 Why Advantages:

If a person knows how to ask good, successive ‘why’ questions, and is able to ask them of the right people, he or she will find at least one root cause for a given problem. This approach takes little time to perform. One needs as few as five minutes to perform a ‘5 Why’ analysis. It does not require the use of special software, flip chart paper, or reading materials. Performing the process repeatedly with the same group of people in a sound manner can lead to a new way of thinking amongst those people that have been exposed to the tool’s use.

5 Why Disadvantages:

The 5 Why approach normally leads to the identification of just one root cause for the problem in question. You will need to go through the ‘5 Why’ process several times for a given problem in order to identify all root causes. To do so effectively requires even more skill of the part of the question asker. It also does not necessarily point the problem solver towards the generic causes of similar problems.

This approach requires significant skill in order to learn how to ask the right why questions. The ‘5 Why’ technique is not as simple as asking ‘why?’ five times. The use of this tool will lead to the definition of a root cause that is also a necessary change (a corrective action). The 5 Why process does not often result in a sound set of corrective actions. Most people fail to gain much success when they use this tool. This is often because they cannot develop the ability to ask good, successive ‘why’ questions. Mr. Shingo could do so with skill, but few others can.

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LISTEN TO my podcast on frequently asked root cause analysis questions!

Evaluating Root Cause Analysis Options: Fault Tree Analysis

Fault Tree Features:

My perspective of fault trees is that they encourage the user to (1) ask the five whys multiple times for a given type of problem and (2) evaluate several possible problem causes on one diagram. This is similar to the manpower, methods, materials, and machines boxes on a fishbone diagram. Like the other common root cause analysis approaches, fault trees are more of an opinion-based tool. Failure mode type and probabilities help you create the tree branches, but no predetermined questions exist.

Fault Tree Analysis Advantages:

From my perspective, I prefer fault trees over fishbone diagrams. Their design allows the user to identify four to five levels of ‘why’ for a given problem, if the users exercise a high level of discipline as they draw their charts. I use fault trees to to troubleshoot persistent problems, such as quality defects. Problems that won’t go away tend to have a common set of causes and sub-causes. A fault tree is similar to the TapRooT® Equifactor tree that one uses to troubleshoot equipment issues.

Fault Tree Disadvantages:

Fault trees typically fail for one of three reasons. First, people do not use them in a disciplined manner to develop multiple problem causes at each level. Second, one must sort through multiple levels of potential causes for each problem type. Third, fault tree results can be opinion driven. They often tend to be a blend of a cause effect diagram and a flow chart. In such cases, the user can easily get lost and not arrive at any particular root cause.

Also, a well-developed fault tree often leads the user to discover that the same management systems (such as poor training, employee turnover, weak communications, and poor procedure design) are at the root of their problems. This is similar to TapRooT® generic causes. A well-designed fault tree may lead you to the TapRooT® basic cause categories. However, its use rarely leads to a comprehensive mix of TapRooT® root causes.

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Evaluating Root Cause Analysis Options: Change Analysis

Change Analysis Features:

I have not seen change analysis called out as a tool for finding root causes by itself. The KT ‘is/ is not’ problem solving tool is the closest thing to change analysis that I have seen. As I stated above, this KT tool is in essence the same as the TapRooT® Change Analysis tool.

Change Analysis Advantages:

It is always useful to compare what should have happened to what did happen when analyzing a problem. This effort alone however will rarely lead you the root causes of, and corrective actions for, preventing the problem in the future.

Change Analysis Disadvantages:

The Change Analysis tool compares what should have happened to what did happen. Comparisons are made across the ‘who, what, when, where, and how’ question dimension to collect information. In turn, use of this tool may not lead you to the actual root causes and corrective actions to prevent problem return.

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Evaluating Root Cause Analysis Options: Fishbone or Ishikawa Diagram

Fishbone Features:

This tool is perhaps the oldest, and most well known, root cause analysis tool. In its most common form of use, the user attempts to define multiple possible causes for a given problem. Possible causes could come from four different areas – manpower, methods, materials, and machines. Teams often use the ‘5 Whys’ technique with this tool to help construct the bones of the chart. The answer to each ‘why’ question results in a new branch off of the previous one that the question originated from.

Fishbone Advantages:

This tool builds on simple list creation. The fishbone diagram serves as a useful tool to capture individual opinions. The team can talk about the information in-hand and identify additional possible causes. In a lot of ways, it is similar to identifying the conditions for a Snapchart, but that is where the comparison ends.

Fishbone Disadvantages:

The fishbone diagram is an opinion-based tool. Its design limits the user’s ability to visually define multiple levels of ‘why’ answers, unless the visual medium in use is really large. Worse yet, users rely on opinion (a vote of some form) to select the most likely causes from the list. Teams then define and test possible countermeasures for the selected causes to see if the problem goes away. This can consume significant time and money. The tool also does not focus on generic cause identification and and elimination.