What is Root Cause Analysis?

Root Cause Analysis

Root cause analysis (RCA) is a systematic, scientific approach to determining the principal cause of a problem. Once the cause is known, it’s possible to find a truly effective solution - one that will stop the problem from happening again, as opposed to merely treating its current effects.

Identifying the real cause of a problem matters. By fixing issues other than the root cause, companies are invariably producing more waste, which is against Lean management principles, and nothing that any company needs.

Root cause analysis is closely linked to Saikichi Toyoda, the father of the 5 Whys technique, used to find the source of a problem. It’s quite fitting to know, that the first Lean company - Toyota, started by Toyoda’s son - was founded to solve the problems stemming from using a manual loom.

But solving problems not only creates new business opportunities. First and foremost, it helps companies to improve and create more value for their clients. The challenge is that, since countless types of problems can occur in any process, there is no one type of solution, or even one way of finding the solution, that works for everyone, every time. Thankfully though, A3 thinking, 5 Whys, Ishikawa diagram, Failure Mode and Effect Analysis (FMEA), and SIPOC are only some of the Lean tools categorized under root cause analysis.

Why turn to Root Cause Analysis?

Typical applications of RCA are a failure to deliver service/product, receiving negative feedback from clients, experiencing a sudden drop in productivity or unplanned downtime. Root cause analysis usually takes a significant amount of time to perform, which can make managers hesitant to use it. The following are a few reasons why applying this approach is beneficial, despite its time consumption:

  • Address the actual problem.
    If companies rush in to find solutions without pinpointing the source of a problem, it leads to an increase in waste and a potential creation of new problems.
  • Unify the team.
    Investigating a problem’s root cause can foster unity between team members, often holding different opinions as to why a problem occurs. Through qualitative and quantitative data, RCA should show the real reasons why an issue or defect presents, helping to establish objective buy-in from all stakeholders.
  • Ensure that the solution is maintained.
    John Foster Dulles, the Secretary of State under Eisenhower said: “The measure of success is not whether you have a tough problem to deal with, but whether it is the same problem you had last year”. RCA allows you to involve the team in determining the true cause of a problem, and therefore lets you ensure that the obstacle does not reappear. It helps to develop solution ownership.
  • Facilitate deeper communication and learning.
    Retrospectives are a great means of gathering information for root cause analysis. Having the team tackle a persistent problem will both bring them together and may lead to improvements outside the scope of the initial dilemma.

How to perform a Root Cause Analysis?

One of the simplest ways to do an RCA is with 5 Whys. The method asks a team to state the problem and then asks “why?” questions until they get to the root cause. Please view this article to see an example of its application.

You can also use a fishbone diagram - to help visualize the problem categories, often following the 5M model: man, machine, material, method, maintenance, together with their potential causes, for subsequent analysis with 5 Whys.

Step 1: Name the problematic effect

Clearly describe how the main undesired effect presents and what parts of the process are affected. This will be shown as the head of the fish on the diagram. Data is vital. Think of how you can quantitatively express the undesired effect and the desired state.

Step 2: Gather data

Now list all the suspected reasons for the problem to be occurring. It’s useful to start with categories, e.g. people, processes, equipment, measurement, management, suppliers, skills, environment, etc, or the 5M mentioned above. The categories are represented by the fishbones connected to the head. At this stage, it’s also useful to gauge the timeline for the issue’s existence: when was the process last functioning correctly, without this unwanted effect?

This can often be the most challenging step - without sufficient data, it will be hard to tell if the identified root cause is valid. Data will also help you establish the baseline with which you’ll be able to later quantify your improvement. Be sure to speak to all workers that experience the problem and gather the available process/material information. If an analysis of the Fishbone Diagram that you’re able to build with that is not giving you the real root cause, then at least it should help you define the areas that need further investigation, before you take another shot at the RCA.

Step 3: Define possible causes

Link all possible and known problem causes under the appropriate category. Look out for any sequences of events that make the problem present, and take a moment to analyze if any specific conditions coexist with the issue. Also, think of whether the problem creates further complications within the process. If so, they need noting down too. At the end of the session, you should have a diagram that resembles the scheme below.

A Fishbone diagram for root cause analysis

Step 4: Identify the root cause

Thanks to the cause and effect graph, you can now select the top couple of reasons and conduct a 5 Whys exercise on them, easily and methodically reaching the heart of the problem. This allows for a true understanding of the nature of the difficulty, the lack of which is very often the reason the issue exists in the first place!

Step 5: Implement a solution

Having access to a complete analysis of the problem, you can design a solution and follow its implementation. You will need to choose a method of solving the difficulty, which will have the least impact on the ongoing production, will maintain a way to measure its success, and will carry the smallest amount of new risk with it.

RCA - not only for solving problems!

Root cause analysis is an exercise useful not only when dealing with problems. Often, an issue will be presented as a business improvement opportunity, and an RCA can certainly be conducted to help identify the key possible areas of change.


  • Dealing with staffing issues - an RCA of those can clearly show flaws in staff performance and highlight the required revisions.
  • Investigating a new marketing opportunity - using the 5 Whys will help stakeholders understand the true nature and potential of the opportunity.
  • Brainstorming a new product iteration - an analysis of the problems the existing product/service is presenting gives direct clues as to what needs changing.

If at the end of your root cause analysis, you can make a problem disappear and reappear by removing and reinstating the cause, you have found the correct solution to your problem. This validation is key. For example, Six Sigma practitioners focus intensely on proving that the root cause was identified correctly before they move on to implementing a solution.

Further reading