Five Whys

When something goes wrong in a facility, it’s best to get down to its root cause rather than simply treating symptoms. However, some problems may not be serious enough to warrant extensive research, which is where the Five Whys method comes in.

What Is the Five Whys Method?

The Five Whys method, also called Five Whys analysis or simply 5Y, is a technique that can be used by maintenance teams to get to the root cause of a problem. It’s easy enough to ask why a problem occurs and arrive at a surface-level cause, but Five Whys analysis requires you to question why that surface-level cause occurred in the first place.

Origin of Five Whys

The method comes from the Toyota Motor Corporation with its founder Sakichi Toyoda. Personnel were told to ask “Why?” five times about any given problem, and as a result, they were able to understand the true nature of those problems.

Ask Why Five Times

The core of the Five Whys method is to look past immediate causes at deeper issues. The process looks something like this:

  • Why did A happen? Because of B.
  • Why did B happen? Because of C.
  • Why did C happen?

And so on until a root cause is discovered.

Tip: An easy way to understand Five Whys analysis is to think about how children ask “Why?” to no end. Each “Why?” digs deeper into the initial problem, and the goal is to understand everything that’s going on.

When to Use the Five Whys Method

Five Whys analysis can be an effective way to get people to look past the immediate causes of issues, but it’s important to use it only when it’s most appropriate. Since it focuses on only a single string of causes and effects, it’s not well suited for complex problems with multiple factors.

As such, Five Whys is best used for the following types of issues:


Simple issues with a single cause don’t require extensive research in multiple directions, which means a single chain of questioning can be used to get to the root cause.

Low Criticality

Less critical processes typically don’t warrant extensive root cause analysis (RCA). Five Whys analysis is a simple way to find root causes without large expenditures in time or resources.

Human Factors

Often, problems arise from human factors, such as operators not performing tasks correctly or preventive maintenance tasks being missed. Five Whys analysis helps maintenance and operations teams determine where existing processes might fail to account for human error.

How to Perform Five Whys Analysis

On the surface, the Five Whys process is very simple: simply ask “Why?” five times to get down to the root cause of a problem. However, there are some best practices to follow to make sure it’s effective. These steps can help you perform Five Whys analysis effectively.

1. Get a Team Together

First, get a team together. Five Whys analysis works best when you have people who are involved in the process where the problem occurred. In addition, including a facilitator in the team can help keep everyone on track.

2. Identify the Problem

Next, identify the problem. It’s important to make sure you define it as specifically as possible, so that everyone knows exactly what you’re trying to solve.

3. Determine Why the Problem Occurred

With the problem in mind, determine the immediate cause for why it occurred. Phrase it as a “why” question, such as “Why does Mixer A keep rumbling?” or “Why does the office air conditioner keep short cycling?”

The answer to this initial question should get you the immediate cause for your problem. For instance, Mixer A might rumble because the lubricant is contaminated, while the air conditioner short cycles because the thermostat is set too high.

4. Ask Why Again

Once you have the immediate cause of the problem, ask why that cause occurs. In our above examples, we’d ask why the lubricant used in Mixer A is contaminated, or why the thermostat keeps getting set too high.

5. Repeat Until You Can’t Go Further

Once you’ve repeated “why” five times, you’ll usually have gotten down to the root cause. However, that’s only a rule of thumb, and it shouldn’t deter you from asking more times if needed. The Five Whys process ends when your questions no longer turn up anything useful.

6. Implement Countermeasures

With the root cause in hand, you’ll be ready to create countermeasures to keep the problem from occurring again in the future.

7. Track the Results

Once you implement your countermeasures, keep tabs on them. By monitoring the results, you’ll be able to tell if you need to adjust them or perform further root cause analysis.

Example of Five Whys Analysis

To really get a handle on how Five Whys analysis works, let’s look at an example.

Defining the Problem

Suppose Awesome Manufacturer, Inc. has a couple machines in their facility that are leaking oil. Their Five Whys analysis would start with getting a team together—likely a handful of maintenance technicians, in this case—and defining the problem. In this scenario, the problem would be stated as, “These two machines are leaking oil.”

Asking Why

With the problem clearly defined, they start asking why it’s happening. The questions and answers might look something like this:

  1. Why are the machines leaking oil? The seals seem to have deteriorated.
  2. Why did the seals deteriorate? They hadn’t been replaced in a while.
  3. Why hadn’t the seals been replaced? The work orders to replace them hadn’t been completed.
  4. Why weren’t the work orders completed? The seals weren’t in stock in our storeroom.
  5. Why weren’t the seals in stock? We ran out before ordering more.
  6. Why did we run out? The Min/Max/Reorder amount for them was set too low in the CMMS.
  7. Why was the Min/Max/Reorder amount set too low? We were trying to keep costs down by setting it lower.

Notice that this particular scenario goes beyond five questions. Again, Five Whys is merely a rule of thumb. You want to keep going until your questions no longer get you anywhere.

Devise Countermeasures

With the above analysis, the maintenance team at Awesome Manufacturer, Inc. can create a solution to the problem. In this case, it would likely be to adjust their Min/Max/Reorder amounts in their CMMS based on mean time between failure (MTBF) rather than expenses alone. Training their team to use MTBF would be an integral part of that process.

They might also come up with additional solutions to further prevent this problem from arising again, such as requiring regular cycle counts, making CMMS data more visible to their storeroom personnel, and displaying process maps in prominent areas.

Keeping Tabs

Once the countermeasures are implemented, the maintenance team at Awesome Manufacturer keeps an eye on the situation, such as by tracking the preventive maintenance work orders for those seals. If any machines start leaking again, that will be a cue to revisit the problem with further analysis.

Tips for Effective Five Whys Analysis

To make your efforts most effective, consider the following pointers when using the Five Whys method.

Solutions, Not Blame

First, and perhaps most importantly, focus your efforts on finding solutions, not placing blame. No matter what process people might be involved in, there will be some incidence of human error. The best way to counteract that is by improving the process to account for that.

For instance, in our example with the leaking seals, it would be easy to blame individuals for not inputting the right Min/Max/Reorder amounts in the CMMS or for failing to perform regular cycle counts. However, the real reason those failures occurred was because there wasn’t a proper system in place to prevent them. The solutions you create through Five Whys analysis should focus on changing systems and processes, not people.

Involve Knowledgeable People

Five Whys analysis relies on the knowledge of those involved. If your team doesn’t have enough knowledge about the problem in question to be able to tell what the causes might be, then you won’t get very far.

When in Doubt, Check It Out

Finally, it helps to use real data and observation when answering each “Why?” in the process. Doing so tends to get you better answers than simply using deductive logic, and it can counteract confirmation bias.

Advantages of Five Whys Analysis

The Five Whys method has a number of advantages for maintenance teams. These advantages include the following.


Five Whys analysis is inexpensive. It doesn’t require you to make a big project out of determining the problem. All you need are a few subject matter experts and a bit of time to explore possible causes, making it ideal for small, low-criticality problems.


The process is easy to follow. All you need to do is define the problem and start digging into why. It doesn’t usually require any fancy tools or software (though those can definitely help), and there’s less need to draw out complex diagrams.

Gets to the Bottom of a Single Issue

By asking “Why?” five times, your team forces itself to look more deeply at a problem than they might otherwise. Rather than stopping upon reaching a surface-level issue, you dig a little deeper until you find a root cause.

Disadvantages of the Five Whys Method

While the Five Whys method has its advantages, it does have a few limitations as well. These include the following.


Five Whys analysis follows a single string of causes and effects, and it’s not really designed to branch out. As such, it’s not well suited to complex issues with multiple contributing factors or for problems that span multiple departments.

Tip: Some organizations solve this problem by using what is called “ Three-legged Five Whys,” in which they branch into multiple paths of causation.

Prone to Bias

The Five Whys method is also prone to confirmation bias. As your team explores the reasons for why a given problem occurred, some may only consider those that confirm what they believe happened. Without outside evidence, the process can quickly devolve into little more than a thought experiment.

Relies on Team Member Knowledge

Finally, there’s a heavy reliance on individual knowledge. If an underlying cause of a problem isn’t known to your team, they aren’t likely to discover it without some extra research.

Five Whys Compared With Other RCA Methods

Five Whys analysis is useful for dealing with the simpler issues that may arise in your processes, but it’s not perfect for every situation. Other RCA tools include fault tree analysis, the fishbone diagram, and FMEA.

Five Whys vs. Fault Tree Analysis

Fault tree analysis works similarly to Five Whys except that it uses a visual diagram to explore multiple causal events. Each branch of a fault tree diagram follows a path of causation, similar to asking “Why?” multiple times in Five Whys analysis.

Five Whys vs. Fishbone Diagram

Another visual way of performing root cause analysis is with a fishbone diagram, also known as an Ishikawa diagram. A fishbone diagram branches into different categories—usually Environment, People, Equipment/Materials, and Procedure—where potential causes are listed. As such, it tends to get more broad than Five Whys, but may not get as deep into individual chains of causation.

Five Whys vs. FMEA

Failure Mode and Effect Analysis (FMEA) is a proactive RCA method in which you look at a process and determine how it might fail in the future. In addition, you look at potential ways those failures could impact different areas of your organization, such as production, safety, and the environment. Put simply, it’s asking “What could go wrong?”

While Five Whys works down from an existing problem to its causes, FMEA looks at how failure in a process could lead to future problems. As such, performing FMEA could help a great deal with future RCA, including Five Whys analysis.

Tip: None of these RCA methods has to be used in isolation. For instance, Five Whys can easily be combined with an Ishikawa diagram or fault tree analysis.


Five Whys analysis is a cost-effective way to find the root causes of simple, one-dimensional problems that may arise in a facility. While it’s ill-suited to complex issues spanning multiple processes or departments, it can be a great way to handle problems that don’t warrant extensive analysis. With a sufficiently knowledgeable team and a bit of data, Five Whys is a useful tool for performing root cause analysis.

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