Machines break down. A critical raw material may be out of stock. Purchase has to be delayed as approval was delayed. The new intern did not turn up on the first day of job. These and many such problems happen at work almost every day. We juggle through these all day fixing one at a time. In a rush for an instant fix, we miss looking beneath the surface. The root cause is not addressed and hence problems reoccur. It becomes a loop. 5 Why analysis is an easy method to dissect a problem and reveal its underlying causes. The following example will illustrate how to use 5 why analysis for problem solving.
Example: 5 Why Analysis for Problem Solving
Problem: There was an unexpected downtime as the machine stopped during production.
First Why: Why did the machine stop?
Answer: There was an overload and the fuse blew.
Second Why: Why was there an overload?
Answer: The bearing was not sufficiently lubricated.
Third Why: Why was the bearing not lubricated sufficiently?
Answer: The lubrication pump was not pumping sufficiently.
Fourth Why: Why was the lubrication pump not pumping sufficiently?
Answer: The shaft of the pump was worn and rattling.
Fifth Why: Why was the shaft worn out?
Answer: There was no strainer attached, and metal scrap got in.
Asking “Why” 5 times helped the team in the example above to link the machine downtime to a missing strainer which let metal scrap in the shaft. Hence the solution here is to attach a strainer to the shaft. Replacing the fuse would not stop the same problem to reoccur. Or checking the lubrication too would not stop the same problem to reoccur.
The trick is to ask “Why” 5 times and answering it each time to uncover the root cause of the problem. Developed by Sakichi Toyoda, the 5 Why analysis for problem solving is part of the Toyota Production System.
The basis of Toyota’s scientific approach is to ask why five times whenever we find a problem … By repeating why five times, the nature of the problem as well as its solution becomes clear.Taiichi Ohno
Why 5 Whys?
The number of Whys depend on the problem. Usually 5 levels of drill down leads us to smaller, manageable root causes. However you may find the root cause after the third why or the fourth why. Or it may take more than 5 levels of questioning to uncover the root cause.
Stop when you find the root cause that does not need further questioning.
The 5 Why analysis for problem solving is one of the simplest tools. It is easy to complete without statistical analysis.
Check this article on isixsigma.com for two 5 Why examples.