5 whys method: a simple technique to reach the root of a problem

What is the 5 whys method and who created it? Toyota’s problem solving philosophy

The 5 whys method is detective work on the process. Repeatedly asking ‘Why?’ allows you to separate superficial symptoms from their real causes. While the first answer often blames human error, the real problem usually lies deeper: in faulty technology or organisational structure. 

The creator of the 5 whys method was Sakichi Toyoda, a visionary and founder of the Toyota Motor Corporation. In the Japanese production system, this technique became the foundation of the Kaizen culture, i.e. the philosophy of continuous improvement and its populariser, Taiichi Ohno, defined it as a scientific approach that avoids looking for culprits in favour of seeking real solutions. This is perfectly illustrated by a classic lesson from the Toyota factory about a sudden robot stoppage on the production line. Instead of settling for a superficial diagnosis that the machine had stopped because of a blown fuse, the team dug deeper and discovered that the overload of the bearing had caused the fuse to blow. Further questions revealed that the overload was caused by insufficient lubrication resulting from a failure of the oil pump, which stopped pumping fluid because its inlet was clogged with metal filings. Ultimately, it turned out that the root cause of the problem was the lack of a filter. If the team had limited themselves to replacing the fuse, the failure would have recurred regularly and only the installation of the missing component permanently eliminated the fault.

How to conduct a 5 whys analysis step-by-step?

This technique is particularly valuable when using the Waterfall methodology. In a traditional, linear approach to management, an error detected at a late stage can generate enormous costs and delays. By repeatedly asking ‘Why?’, the team is able to precisely diagnose at which point in the rigid process the mistake occurred. This allows changes to be made to standards before moving on to the next phase, which in a waterfall environment is crucial for maintaining the integrity of the entire project.

Even though this technique seems super simple at first glance, how well it works depends on how disciplined the team is and how thorough the analysis is. Instead of just going with their gut, leaders need to base the process on hard data and direct observation of what’s really going on. To do a good cause-and-effect analysis, you need to follow these steps:

• Precise definition of the problem: the key to success is to assemble a team directly related to the problem and describe the issue with specific data. Avoiding generalisations in favour of facts (e.g. ‘15% of shipments delayed this week’) allows the team to focus fully on the right challenge.
• Identifying the immediate cause: the first question, ‘why?’, serves to identify the most immediate reason for the error. At this stage, it is important that answers are based on verifiable facts and observations, excluding subjective assumptions.
• Exploration of root causes: by repeating the question multiple times (usually five times), the analysis is deepened. The goal of the process is to arrive at a cause that the organisation can realistically influence.
• Verification of logic (the ‘therefore’ test): the consistency of the conclusions drawn is checked using a reverse logic test. This involves combining the answers with the phrase ‘…and therefore’. If a sequence such as ‘No work standard and therefore an operator error occurred’ sounds logical, the analysis has been carried out correctly.
• Implementation of corrective actions: the final stage focuses on designing and deploying changes specifically engineered to eliminate the identified root cause. To ensure the process reaches a successful conclusion, it is vital to produce a clear executive summary that translates strategic decisions into actionable steps. This involves the assignment of specific tasks, the designation of responsible individuals to lead each initiative and the establishment of binding deadlines. 

Common mistakes when asking ‘why?’ during root cause analysis

Even such an intuitive method can lead to erroneous conclusions if the team falls into typical cognitive and organisational traps during the analysis. Here are the most common mistakes:

• Looking for someone to blame: focusing on the person (‘the employee made a mistake’) instead of the lack of standards, training or process safeguards.
• Leading questions: asking accusatory questions (e.g., ‘Why didn’t you make sure of that again?’), which prevents honest analysis.
• Ending too quickly: stopping at a superficial answer (e.g. ‘the machine broke down’) without investigating the technical or organisational causes.
• Relying on assumptions: failure to verify the facts.
• Too general answers: phrases such as ‘because there is not enough time’, which do not indicate a specific element of the process that needs improvement.

5 whys in project’s manager’s practice – analyzing delays and recurring projects issues

In the work of a project manager, the 5 whys method provides invaluable support in the rapid analysis of incidents, sprint delays or budget overruns. Mastering task management in projects – how to plan, delegate & monitor progress, is an essential foundation, but it is the “5 Whys” technique that allows you to understand why those plans sometimes fail. Proper application of this tool enables you to avoid costly corrections and eliminate recurring errors that hinder progress once and for all.

The power of this tool is best illustrated by the example of a website construction project that was delayed by six weeks. When looking for the cause, it can be seen that the deadline was pushed back because the mock-up design phase took much longer than originally planned. This was due to the fact that the client repeatedly requested significant changes to the concept during the work. Digging deeper, it turns out that the root cause of the problem was the lack of detailed requirements and scope of the project at the very beginning. This situation arose because the schedule did not include a discovery workshop with key decision-makers, which meant that the most important initiating document, the project charter, did not contain a precisely defined scope. The final analysis leads to the root cause: the company’s standard bidding process simply lacks a mandatory phase of clarifying requirements before signing the contract. With this discovery, the project manager can take specific and effective corrective action. Instead of just putting out fires in the current order, they introduce a discovery workshop into the regular sales process and implement clear change management rules.

Combining 5 whys with other methods (e.g.,Ishikawa Diagram)

Although the 5 whys method is extremely effective, when used in isolation it can sometimes limit the team to a single, random path of analysis. To mitigate this risk and ensure a comprehensive approach, it is essential to treat this technique as a cornerstone of flexible project management: key strategies for successful projects. By combining the 5 whys with an Ishikawa diagram – often referred to as a ‘fishbone’ diagram – managers can achieve a much more robust diagnostic framework. In this arrangement, the Ishikawa diagram provides the necessary ‘breadth’, categorizing potential causes such as people, processes, technology, or machinery, while the 5 whys method provides the ‘depth’ required to reach the source of an issue.

In practice, this synergy functions much like a mind map, allowing teams to visualize connections between different operational areas without overlooking critical threads. By first brainstorming the Ishikawa structure and then applying the 5 whys to its most significant branches, teams avoid settling for surface-level hypotheses. This methodology aligns perfectly with A3 reporting standards and the PDCA (Plan-Do-Check-Act) cycle. Ultimately, this integrated strategy allows for the planning of corrective actions that realistically and permanently improve KPI indicators and organizational procedures across the board.