The 5 Whys: Question-Based Root Cause Analysis

The important thing is not to stop asking questions.

Albert Einstein

The 5 whys, why-why or ladder of whys, is a technique that allows you to find the root cause of a problem. It is no more.

There is no science involved in the approach, but because we try to get as specific as possible with each item, we will go into additional depth to dispel any lingering questions about how to use it.

Today, we’ll discuss a method that is frequently employed. You’ve probably heard of it or maybe used it without realizing it was a specific tool.

Its originator, according to legend, was Sakichi Toyada. It was used as a crucial element in the solution of the manufacturing issues faced by the Japanese automaker.

Later, the technique was continued by Taiichi Ohno:

Observe the production shop floor with no preconceived ideas and a blank mind. Repeat “why” five times for each issue.

What are the 5 Whys?

5 why’s is a cause-effect analysis tool that works through questions.

By asking oneself “why,” we can analyze a situation using this strategy. After receiving the response, we must once more question why?, and so on.

5 whys: Application examples

Example #1: Toyota Case

The first is an example proposed by none other than Toyota.

A machine has a malfunction

• Why did the machine break down? BECAUSE the fuse blew due to an overload.
• Why was it overloaded? BECAUSE the bearings did not have sufficient lubrication.
• Why did they not have enough lubrication? BECAUSE the lubrication pump was not circulating enough oil.
• Why was the pump not circulating enough oil? BECAUSE the pump was clogged with metal shavings?
• Why was the pump clogged with metal shavings? BECAUSE the pump does not have a filter.

So, a dirt in the pump due to the lack of filter generated an overload in the fuse which finally caused the breakdown of the machine. In this example each cause brings its own effect, so acting on the fifth why, should solve the root of the problem.

Example #2: Staff replacement

The system is displaying outdated customer point data.

1. Why is the system displaying outdated data? Because the analyst did not upload the previous month’s points.
2. Why didn’t the analyst upload the previous month’s points? BECAUSE nobody taught him how to do it.
3. Why didn’t anyone teach him how to do it? BECAUSE no one knew the procedure and the person who did know the procedure quit.
4. Why didn’t anyone know the procedure? BECAUSE the previous person did not explain it to anyone and it was never documented.
5. Why was it not explained to anyone or documented? BECAUSE there was no estimate of the likelihood that a critical person would or would not be able to leave the company, their difficulty of replacement, and the complexity of the procedure.

In this example, what appeared to be a software problem ended up being a human problem whose background is much more relevant than it appears.

The correction comes out in the first why: to load the previous month’s points; how? We will have to check with the software developer as no one knows how. However, the root cause of this problem reveals a much more important problem: the criticality of the job positions has not been defined, so there is knowledge in the staff that has not been documented.

Example #3: Theft

It is evident that tire purchase costs have increased in the last 8 months.

1. Why has the cost of purchasing tires increased? BECAUSE tires last half as long as they used to and now it is time to buy them sooner.
2. Why do they last less? BECAUSE the new tires never came in, the old ones are still being used but new ones are being purchased.
3. Why do people keep using the old tires and keep buying new tires? BECAUSE the business leader is selling the new tires that come in, plus he is getting money from the maintenance shops for taking care of the damage to the old tires more frequently.
4. Why didn’t we notice? BECAUSE we don’t track the estimated life of the purchases or compare it to their actual life.

This example is quite unique. In this case, 4 Whys? were enough to get to the root of the problem, although the correction of the problem is evident in the “third why”; “kicking out” the business leader, as it is a clear case of theft.

However, firing the process leader does not get to the root of the problem and leaves open the possibility that the next person in the position will also engage in this practice, so calculating the estimated duration of certain purchases and tracking their duration is imperative.

Advantages of the 5 why’s

After understanding the instrument, we can already see the benefits it offers. Here are some of them:

• It enables thorough exploration of a problem’s nature over numerous iterations.
• Its use is really straightforward.
• It fosters cooperation.
  In fact, it ought to be used by those who are familiar with the phenomenon being studied.
• It works in conjunction with other methods like Ishikawa analysis.
• The primary benefit is that it addresses the problem’s underlying causes and stops it from recurring again.

Other interesting links about the technique

• Buffer: Buffer is a service for managing social media accounts in an integrated way. You will find how they have applied the technique to solve problems. Very detailed cases in English.

Image source: The featured image in the post was downloaded from Freepik.