The 5 Whys technique offers a simple, effective way to uncover the root of an issue. It is best used in simple troubleshooting and quality-improvement initiatives.
Start with an issue and question why it is happening. Ensure the answers are grounded in fact, and then ask the “why?” question again. Continue the process until the root cause of the problem is reached, then identify a solution that will prevent the original issue from recurring.
Where did the 5 whys technique come from?
The founder of Toyota Industries, Sakichi Toyoda, developed the 5 Whys technique in the 1930s. It gained popularity in the 1970s and is still used by Toyota to solve problems today.
Rather than relying on a decision from a boardroom, the 5 Whys was intended for use by the people on the shop floor – the people doing the job.
When should I use the 5 whys technique?
The 5 Whys technique has a few uses, from quality improvement to troubleshooting, but it is best used to resolve simple to moderately complex issues.
5 Whys probably isn’t well suited to assist in a complex or a critical issue, because it tends to isolate a single “root” cause solution, when there may be more than one failure cause.
Because of its ability to easily isolate a single root cause, the 5 Whys technique is recognized as a simple, flexible tool, which can combine well with other methods such as Lean and Six Sigma.
How do I use the 5 Whys technique?
The 5 Whys technique is simple enough for an adequately trained individual to apply it on their own, but like all problem-solving processes, solutions tend to be better when a diverse group of people are involved in the process.
When applying 5 Whys in a group environment, the 5 Whys technique uses a six-step process:
1. Assemble the team.
Ensure the team assembled are experienced with the intricacies of the issue. Someone should be the facilitator. The facilitator keeps the team focused on the task in hand.
2. Define the problem.
Try to watch the issue in operation. Talk to the team and have a clear issue statement written, one which all of the team agrees with. An example could be “Pump X is vibrating”.
Using a whiteboard or a sticky note, write the statement, leaving sufficient room around the statement to add the repeated Whys.
3. Ask the first “why?”
Ask the team why the problem is occurring. In this example, “Why is Pump X vibrating?”
This sounds simplistic, but it should take the team a lot of thought to arrive at answers which are both realistic and were actually present at the time the event occurred. It is important to remove guesswork from the answers.
Try to avoid jumping straight to conclusions or the solution. It is important that there is a logical connection between each of the answers.
Record on the whiteboard/sticky notes any possible reasons the team has come up with. Ensure that a phrase rather than a single word is used. “The motor tripped” is better than just “overloaded”.
4. Keep asking “why?” until the root cause is identified.
Ask four more “whys?” in succession. Each time ensure the “why” question is aimed at the previous response. Ensure each question is dealt with as quickly as possible, so that a full picture of the issue is formed, limiting jumping to conclusions.
The name “5 Whys” is basically a guide. It may be required to keep asking “why?” until you reach the root of the issue. It may also be that you reach the root before the 5th “why?”
The important thing is to keep asking “why?” until you stop finding useful responses.
5. Address the root cause.
Once the team is happy that the root cause has been identified, it is time to discuss and implement the agreed solution to the issue.
6. Monitor the solution.
As with any good system, once the solution is in place, monitor the issue to ensure the solution addresses the initial problem.
Limitations of the 5 Whys technique
One of the limitations of the 5 Whys technique is that it tends to lead you down a single path to a solution. This is particularly challenging when there may be many different answers to the question “why?” at each level.
An example of a single path investigation is as follows:
Problem: Pump X is vibrating.
The pump is cavitating, causing it to vibrate.
Insufficient media is entering the pump.
The feed tank is empty.
There is insufficient product in the tank to keep the pump suction submerged.
The pump is sucking more product than the tank can deliver.
The pump VSD is set too high.
Note that in the above example, another possible answer to the second “why” is that the density of the feed is too low, or that the inlet to the pump is blocked.
In these situations, the 5 Whys technique may be able to be enhanced by combining it with another problem-solving technique, such as a fishbone (otherwise known as an Ishikawa) diagram. For more complex problems, a full cause-effect diagram may need to be used.
If you are looking to expand your capability in root cause analysis and defect elimination, consider reading some of our other articles on these topics: