Best Tools for Root Cause Analysis

There are two basic ways of dealing with issues:

  1. We can react quickly when an issue occurs so that it will not stop or delay the normal flow of events. The goal of this method is to provide a speedy fix to normalize the situation as soon as possible.
  2. Another way is to perform a thorough investigation after an issue has occurred. We try to get as much information as we can, analyze it, and come up with solutions that would prevent the issue from recurring. The goal is to arrive at an accurate and precise understanding of the issue, so that the exact, long-term fix can be implemented.

The first problem solving technique deals with the visible symptoms of an issue, while the second employs root cause analysis to fully understand the issue in order to solve it.

Root cause analysis

Root cause analysis (RCA) is a problem-solving method used in proactive management. When issues and problems occur, the main, fundamental, underlying, deepest, or root cause of the problem does not present itself most of the time. What are more visible are its manifested symptoms and causal factors. Although finding a solution that addresses symptoms can be quicker, it will almost always not solve the problem, because the initiating cause is not addressed.

Example of symptoms vs root cause

A manager notices a puddle of water on the floor of a factory. That is a safety hazard that should be addressed. He asks the supervisor to have a maintenance personnel get a mop and clean the puddle. The manager makes a note of ordering more mops for the factory. The visible symptom of the problem—the puddle—is dealt with.

The supervisor, however, is curious about the puddle as it was not there the day before. She investigates and discovers that the puddle came from a leak in one of the factory pipes. She searches further and discovers that the pipe leaks because the water pressure in the pipe is too high. The high water pressure is brought on by a faulty pressure valve. Her investigation stopped there because she could not get more information on why the valve is faulty. She then recommends that the valve be replaced. This normalizes the water pressure to a level that the pipes handle well, and no more water leaks to create a puddle on the floor.

While the manager addressed the symptoms of the issue, his quick fix means that the puddle will return, and the company would eventually spend unnecessary money purchasing monthly supplies of mops. The supervisor’s deeper investigation means that the company fixes the problem for the price of a new valve.

Best tools for root cause analysis

There are several tools used in root cause analysis, and they are applied in many fields such as systems analysis, IT, telecommunications, manufacturing, health and medicine. Some can be applied to simple problems while others are ideal for more complex and layered problems. Here are a few of them:

5 Whys

The 5 Whys is a simple tool where you ask the question ‘why is the problem happening’ or similar variations as many times as possible until you can no longer answer it. You are not limited to asking up to 5 times—it may be fewer or more until you arrive at the level where you cannot come up with answers anymore, just like the water puddle example above. This method does not guarantee you will find the root cause, but is an effective analysis tool to go beyond symptoms. A good strategy is to use a Pareto chart first, which will help you focus on the 20 percent of defects that usually cause 80 percent of the problems.

Is/Is Not Analysis

Another simple RCA tool is the Is/Is Not analysis. It is a good tool to help you focus on the probable root causes. You first state the problem or the situation. Using a table, create one column for questions, another column labeled ‘Is’, and a third column labeled ‘Is Not’. On the first column, write questions like what, where, or when, and provide answers for the Is and Is Not columns. For example, using our water puddle example, we can answer that the puddle Is water, and Is Not oil. The puddle Is on the factory floor, and Is Not on the conveyor. These answers narrow down the source and location. This tool eliminates non-related, untrue causes, so you can focus on the right ones.

Failure Mode and Effect Analysis

The FMEA process analysis tool is ideal for analyzing the design, manufacture or assembly of systems with known components. On a spreadsheet, you list all components, parts, or steps and describe how that component may fail. It can be an error or a defect, potential or actual. For every failure mode, describe also the consequences or effect. FMEA is a systematic, structured approach that allows you to anticipate what can go wrong and its impact to the whole system, product, or process. It can also be used in reverse when an issue occurs to narrow down the specific causes or components that failed.

Affinity Diagram

The affinity diagram—also known as the KJ method—is an organizational tool best used after brainstorming. When you have a large number of ideas after a brainstorming session, you need to narrow them down and group them together to prevent duplication and redundancy. To build the diagram, you first have to record all the ideas into separate cards or notes. Next, the team should look for ideas that are related and group them together. All cards must be sorted and belong to a group. The benefit of the process is becoming very familiar with the data to know which ideas belong to a specific group. The affinity diagram can serve as an input to a fishbone diagram.

Fishbone diagram

A fishbone diagram—or cause-and-effect diagram—is ideal for complicated problems. It takes into account multiple categories of causes that created the problem. Root cause analysis does not limit to the identification of a single root cause. It is possible that several root causes are present. In a fishbone diagram, categories such as people, environment, machines, materials, and methods are listed. As the team brainstorms why the problem happened, the answers are listed under one or several categories that might be the probable cause. Teams can then use the 5 Whys to arrive at the lowest level of causes they are aware of.


Root cause analysis is an effective process but only as effective as the effort given to find the answers. Some of the challenges include:

  • Writing accurate and descriptive problem statements
  • Getting enough supporting data
  • Presence of multiple root causes
  • Not having enough perspective

In problem solving, more heads are usually better than one, so a team effort goes a long way. It is sometimes easier to make assumptions when data is not available, but this can be risky. Using additional tools such as fault tree analysis or scatter plots can help you get a more accurate understanding of the problem. Also, root cause analysis should pave the way for corrective action that is well planned and executed.

Jose Maria Delos Santos

Jose Maria Delos Santos

Jose is a subject matter expert and member of the writing team for and Bridge24. He has written hundreds of articles including project management software reviews, books reviews, training site reviews, and general articles related to the project management industry.

Leave a Reply