How to Conduct a 5-Why

Mark Galley

this blog post was updated on 09/10/2021.

5-Why Cause Mapping® Root Cause Analysis

With a few minor adjustments, conventional 5Whys can significantly improve the way organizations communicate and solve problems. Knowing how to ask why questions and then organize the answers is an important part of digging into an issue. There are strong views on the usefulness of conventional 5Whys. Some organizations strictly adhere to the approach. Others think it’s too simple and provides no value. Cause Mapping root cause analysis makes changes to the traditional 5Whys tool that simplifies the documentation, organizes the causes more clearly and allows the analysis to expand into a 10- or 15-Why if needed.

What is 5Whys?

Conventional 5Whys is a part of the problem-solving toolkit for most quality groups. It’s used within Kaizen, lean and six-sigma. The concept is simple. It starts with a problem that gets broken down with a series of why questions. The answer to the question, “Why did this happen?” is the basis for the next why question. This continues five times.

Toyota is typically cited as establishing 5Whys as a formal method almost 100 years ago. But if you’ve ever had a 3-year-old in your life you’ve experienced recurring why questions. A three-year-old asks why questions because they want to understand things. This same approach will work for your organization too. More on the "criticisms of the 5-Why approach."

5Whys Purists

Those who subscribe to conventional 5Whys apply it literally. They write sentences down the page and consider the answer to the fifth why question to be the root cause. Their mental model is that the fifth cause is special because the problem can be eliminated if that cause is solved. It seems to work so perfectly, but things are not as they seem. Any one of the causes before or after the fifth why can have even better solutions.

There is nothing special about the number five. Asking why questions is part of explaining an issue, but there’s no reason to limit the analysis to five. A few why questions are a great way to start an analysis, but depending on the magnitude of the issue, more causes may need to be revealed. A 5-Why Cause Map diagram is only a phase of an investigation that can expand into a much more detailed analysis.

Anti-Why Crowd

Some individuals don’t like why questions. They think it yields too many different answers and makes people defensive. Some feel 'how' is a better question. But 'how' and 'why' are both used to identify cause-and-effect relationships. They go hand in hand when explaining something. Cause-and-effect relationships supported with evidence are what explain how things work: how a smartphone works, why hot air rises, how pain medication blocks receptors, why the tides move in and out, how an injury occurred and why the equipment failed. Accurately explaining cause-and-effect relationships is the basis of a scientific approach.

Unfortunately, some organizations overlook this basic principle. They think problem-solving is a combination of tools, techniques and terminology. They believe a problem-solving method provides structure to the incident – like a Fishbone or 5Whys. In contrast, a Cause Map diagram reveals the structure that is already within the incident. There is no secret sauce or technique for explaining a problem; there are basic principles.

"Why" Questions are Fundamental

A why question is an easy way to identify a cause-and-effect relationship. And it is cause and effect that explains how things happen. All problem solving happens within the domain of cause and effect. Why a specific solution was effective or how your operations work is all explained by cause and effect. It’s the basis of all problem-solving and troubleshooting. People sometimes miss important signals within their operations because they aren’t asking enough why questions. The ability to ask and answer why questions is essential for understanding both the things that go badly and the things that go well.

Benefits of 5-Why Cause Mapping® Root Cause Analysis

Three advantages of building a 5-Why Cause Map diagram for an issue are that it’s easy to get started, quick to layout and even though it’s basic, it can expand into as much detail as needed. Cause and effect is easy to understand and can be applied to any type of issue. It doesn’t change from incident to incident. A simple 5-Why Cause Map diagram is not a comprehensive analysis, but it’s a great way to begin. Regardless of how complex the issue is, the analysis can begin with just one or two why questions, then expand as needed. A 5-Why Cause Map diagram is just an initial phase of a more thorough investigation.

Don’t Write Sentences - Make a Diagram

The conventional approach for documenting 5Whys is sentences written down the page. They’re typically numbered from one through five. Writing a sentence, then asking a why question and writing down another sentence can take too many words. Cause-and-effect relationships are much easier to show as a diagram. We suggest building a 3- to 5-Why using Cause Mapping root cause analysis. Each cause is written in its own box. It lays out horizontally across the page with an arrow pointing to the left, from the cause to the effect.

The Toyota Welding Robot example shows a conventional 5Whys written in sentences using 81-words. The same issue is built in a 5-Why Cause Map diagram with only 31 words. Test this approach on some of your problems or contact us for help.

5-Why Cause Map Diagrams Do Not Need to be Repeatable

One of the criticisms of conventional 5Whys is that it’s not repeatable. Different people build different 5Whys. This criticism reveals the confusion about the basics of cause and effect. Different people naturally build different analyses because different people see problems the different ways—they have different backgrounds and areas of expertise.

Some people argue that 5Whys is not scientific because it’s not repeatable, but their premise is flawed. Three people can make three different 5-Why Cause Map diagrams that all combine to into one, more complete explanation of the issue. If each 5-Why Cause Map diagram is built accurately, they’ll combine without any contradiction. This is much easier to demonstrate using an example. The Titanic 5-Why video shows how three different 5-Why Cause Map diagrams build into one, accurate 9-Why Cause Map diagram. This works precisely because of cause and effect.

Improving the Improvement Tool

Expanding a 5-Why Cause Map diagram is simple, but it’s not what conventional 5Whys teaches. Most 5Why users have been taught to restrict the analysis to five questions. Starting an investigation as a 5-Why Cause Map diagram is smart. Limiting it to a 5-Why is not. It’s another example of how a prescriptive method can alter the explanation of an issue.

A problem-solving method should not distort an issue. It should reflect it. A map of your town should look like your town. A Cause Map diagram of your problem should look like the issue – regardless of what level of detail you reveal—5, 15 or 25 causes. All the different Cause Map diagrams for an incident are accurate, they’re just at different levels of detail. Don’t limit the clear explanation of your problems. Experiment with this approach on some problems in your company and reach out to us if you need any help trying it out.

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