Introduction to the 5 Why and the 5 How

Have you ever had a problem that kept recurring? Having to deal with a problem or failure mode more than once is a waste of time and valuable resources. The problem is that the root cause is not identified or addressed. If the root cause is not reached, then you are simply treating a symptom of the problem. Furthermore, if a permanent solution is not determined and implemented, the problem will eventually recur. There is an easy-to-use tool that can help eliminate recurring problems. This tool is the 5 Why and 5 How. The 5 Why and 5 How were developed in 1930 by Sakichi Toyoda. Mr Toyoda is the founder of Toyota Industries and is said to be one of the fathers of the Japanese industrial revolution. This technique gained popularity during the 1970s and is still used by Toyota and other companies and organisations today.

What are the 5 Whys and the 5 Hows

The 5 Whys method simply consists of asking the question "Why" enough times until you get through all the symptoms of a problem and get to the root cause. The 5 Whys method is often used during the analysis phase of the DMAIC process and the planning phase of PDCA activities. It is often used in coordination with other analysis tools such as the Cause and Effect Diagram but can also be used as a stand-alone tool. 5 Why is most effective when answers come from people who have practical experience of the process under consideration. By repeating the "Why" question, one can get to the root cause of the problem.

The 5 How are then used to determine a radical or permanent solution to the 'root cause of the problem'. The 5 whys and the 5 hows have also been described as a ladder. One moves up the ladder using the 5 whys to arrive at the root cause and then moves up the ladder using the 5 hows to arrive at the problem resolution. The team will examine "Why" the problem occurred and "How" it can be solved so that it does not happen again.

Example of the 5 whys and the 5 hows

How to perform the 5 whys and the 5 hows

Forming the team

Exercise 5 Why and 5 How should be performed by a cross-functional team (CFT). It should not be done alone at one's desk. The team should include representatives who are familiar with the process in question together with members from quality, process engineering and operators from different shifts or the next stage of the process. Each team member will bring his or her own unique perspective on the problem and ask important questions that might not otherwise have been asked.

Defining the problem

The first thing every team should do during a root cause investigation is to clearly define the problem. Develop a clear and concise statement of the problem. The team should focus on the process and not the personnel. The team should also determine the scope of the problem to be addressed. If the scope is too narrow, the problem solving exercise may lead to small improvements when larger and more extensive improvements are needed. Conversely, defining the problem with too broad a scope could extend the time needed to solve a problem and generate solutions that may not fit the corporate culture or align with corporate strategy and never be realised. When you take the time to clearly define the problem in advance, you often save time and make it easier to solve the problem.

Ask why

Next, the team leader or facilitator should ask "why" the problem or failure mode occurred. Answers should be supported by facts or data and not based on an emotional response. Answers should also focus on process or system errors.

The facilitator should then ask the team whether the identified causes have been corrected, the failure mode or the problem could still occur. If the answer is yes, then move on to the second "Why" and then to the third, fourth, fifth and so on until the answer is no.

Note: It is not always necessary to ask "Why" five times. The root cause may be identified during the third or fourth 'Why'. It may also take more than five times to get through the symptoms of the problem and arrive at the root cause. Also, at the third, fourth or fifth 'Why', a systemic or management practice may probably be discovered as the cause.

Determine and implement corrective actions

Once the root cause has been determined, a list of appropriate corrective actions should be developed to address each root cause. The 5 How is a useful method for brainstorming solutions to the root causes and developing actions to solve the problem. The facilitator should ask for the 5 How related to the problem at hand. How can this cause be prevented or identified? Keep asking "How" until you come to the solution that solves the root cause. Actions should have an owner and an expiry date. Regular meetings should be held to update the team on the status of the actions until all are completed. Upon completion of the recommended actions, the effectiveness of the actions should be determined. The process could be monitored and measured using statistical process control (SPC), parts inspection or other methods to validate the effectiveness of any improvements.

Example of the 5 Whys

There are various formats used to document the exercise of the 5 Whys, some more detailed than others. The following is an example of the basic process of the 5 Whys.

Statement of the problem - An operator fell and injured himself during the start of the first shift.

• Why? There was an oil leak on the floor in the processing department.
• Why? A gasket on machine 3 deteriorated and started to crack and leak oil.
• Why? The gasket material was not suitable for the machine and the type of machining.
• Why? Cheaper seals purchased from a new supplier.
• Why? The gasket material was not specified in the service manuals.

Care must be taken to ensure that the 'whys' follow a logical path. One method to check whether the progression follows a logical path is to read the causes in reverse order. When reading the causes or 'whys' in reverse order, they should follow a logical progression towards the problem statement or failure mode. Referring to the example above, the progression would be this:

Gasket material specifications are not listed in the service manual

• So - Gaskets were purchased cheaply from a new supplier to reduce costs
• So - The gasket material was not suitable for the machine and the type of processing
• So - A seal in machine 3 deteriorated, cracked and started to leak
• Therefore - There was an oil spill on the floor
• Therefore - An operator slipped and fell and was injured during the first shift

The Three Legged 5 Why

It is not uncommon for the problem to have more than one root cause. The progression of the five causes sometimes branches off to form more than one path. In many cases, the root cause occurs due to an ineffective detection control or a systematic problem within the organisation. The Three Legged 5 Why includes additional pathways to determine which control or process was not in place or was not effective enough to detect the failure prior to the incident. Systemic or management processes that were not in place or may have contributed to the incident are also examined.

The 5 Why / 5 How method is one of several Root Cause Analysis (RCA) tools available for use in problem solving and continuous improvement activities. If you would like more information on the 5 Why / 5 How method or other RCA tools, please contact one of our highly qualified and experienced professionals at Iatf16949. Your success is our business!