What is a Fishbone Diagram?

What is a Fishbone Diagram?

The fishbone diagram is a visual representation of the cause and effects of a problem. Through constructing the diagram, teams come to articulate an issue, which makes finding the cause of the problem easier.

Fishbone diagrams are also known as Ishikawa or cause-and-effect diagrams. They are a great means to understanding a problem.

Emphasizing the understanding of a problem is innate to Lean philosophy, and can result in finding better solutions to real issues, which would otherwise be causing ripple effects across the process. In short, through the application of the collective knowledge of all partaking subject matter experts, it helps with addressing the right problems.

When is a fishbone diagram used?

This type of analysis has utility in all business activities, from risk analysis, through product design to project management, as well as for quality control. Furthermore, by looking through all potential tensions and imperfections in the present systems, you can identify future issues, before they become big enough to cause mayhem to the process.

Though the cause and effect diagram, with commonly used complementary techniques such as 5 Whys or Pareto charts, will help you spell out the source of a problem, it will not always be of great help with resolving it, especially if your process is highly complicated. For that part, you should turn to planning a solution with a flowchart, or with good old team brainstorming, during which anyone can come up with ideas, while a leader will choose the most appropriate ones.

How to use a fishbone diagram?

The diagram’s components are very simple - the head of the fish is the effect or problem, that is being discussed, with bones attached to the spine being the categories of issues, and smaller bones the issues themselves.

Step 1: The head: name the problem

Show the problem to be worked on as the head of the fish, with a line running from the head to the tail. If the matter at hand is a problem, its definition should be accurate and objective. And if you’re drawing the diagram to plan a change, or analyze a new design, make sure to formulate the goal at the head clearly, and to make it achievable.

The fishbone diagram works on the assumption that most undesirable effects are linked to several categories of causes, but that just one or two of these causes will be the reason for the problem (Pareto principle), hence dealing with these few causes alone should alleviate the issue.

Fishbone diagram - the head

Step 2: The scales: name the categories

List the categories in which the major causes lie as the scales of the fish. Typical categories would be materials, machines, method, measurement, or manpower. They show the diagram’s close relation to the 5M model. However, there can be many more categories of causes, and you should match them to your specific case.

Fishbone diagram - the categories

Step 3: Fishbones: name the causes

The categories of causes are positioned around the spine of the fish and linked to it through large fishbones. Now, list the supporting causes under the relevant category, drawing smaller fishbones.

Example

Fishbone diagram - the problems

In this example, the method was not articulated, and people were lacking direction, which resulted in no project management efforts and a lack of clarity for the team - both delaying the project. However, no team and process management effort can fix a broken machine, nor resupply the process with materials. Hence, these 2 problems must be addressed first. Then, the lack of a method can be looked at, to ensure that proper communication and reporting takes place, for on-time project delivery.

By naming both the possible and factual causes of the problem, the team should get closer to finding out the true cause of the situation they’re in. Listing them all makes it easier to check what has and has not been done, and to locate the true source of the difficulty.

Creating a comprehensive fishbone diagram, visualizing all of the caveats of your process, all aspects, all the steps, all prescribed efforts, will help you to better understand the way your team works and streamline it, where necessary, thereby decreasing variation. This alone will improve the way you work, alongside your customers’ experience. You’re welcome to learn more about why variation reduces productivity here.

Don’t swallow the whole fish at once

Similarly to how you wouldn’t eat an entire fish in one go, but rather piece by piece, you should also look at the diagram’s elements one by one, starting with the one that has the most meat on it. The most wasteful thing to do would be to launch an initiative that attempts to solve all the problems at once - manpower, method, machine, and material components. The result would be with the initiative getting choked, rather than tackled step by step.

What are the benefits of using a fishbone diagram?

  • the ability to solve problem causes, not just their symptoms
  • quick identification of process bottlenecks
  • promotion of teams’ problem-solving skills growth
  • the possibility of seeing the relationship between different problems, as well as between their solutions

However, it’s worth keeping in mind, that fishbone diagrams are not easily applicable to complex problems, where causes and effects can be too difficult to spot in a dense criss-cross of symptoms across all process categories.