Cause and Effect Analysis
Identifying the Likely Causes of Problems
(Also known as Cause and Effect Diagrams, Fishbone Diagrams, Ishikawa Diagrams, Herringbone Diagrams, and Fishikawa Diagrams.)

Find all possible problems.
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When you have a serious problem, it's important to explore all of the things that could cause it, before you start to think about a solution.
That way you can solve the problem completely, first time round, rather than just addressing part of it and having the problem run on and on.
Cause and Effect Analysis gives you a useful way of doing this. This diagram-based technique, which combines Brainstorming with a type of Mind Map, pushes you to consider all possible causes of a problem, rather than just the ones that are most obvious.
We'll look at Cause and Effect Analysis in this article.
About the Tool
Cause and Effect Analysis was devised by professor Kaoru Ishikawa, a pioneer of quality management, in the 1960s. The technique was then published in his 1990 book, "Introduction to Quality Control."
The diagrams that you create with Cause and Effect Analysis are known as Ishikawa Diagrams or Fishbone Diagrams (because a completed diagram can look like the skeleton of a fish).
Cause and Effect Analysis was originally developed as a quality control tool, but you can use the technique just as well in other ways. For instance, you can use it to: * Discover the root cause of a problem. * Uncover bottlenecks in your processes. * Identify where and why a process isn't working.
How to Use the Tool
Follow these steps to solve a problem with Cause and Effect Analysis:
Step 1: Identify the Problem
First, write down the exact problem you face. Where appropriate, identify who is involved, what the problem is, and when and where it occurs.
Then, write the problem in a box on the left-hand side of a large sheet of paper, and draw a line across the paper horizontally from the box. This arrangement, looking like the head and spine of a fish, gives you space to develop ideas.
Example:
In this simple example, a manager is having problems with an uncooperative branch office.
Figure 1 – Cause and Effect Analysis Example Step 1
(Click image to view full size.)

Tip 1:
Some people prefer to write the problem on the right-hand side of the piece of paper, and develop ideas in the space to the left. Use whichever approach you feel most comfortable with.
Tip 2:
It's important to define your problem correctly. CATWOE can help you do this – this asks you to look at the problem from the perspective of Customers, Actors in the process, the Transformation process, the overall World view, the process Owner, and Environmental constraints.
By considering all of these, you can develop a comprehensive understanding of the problem.
Step 2: Work Out the Major Factors Involved
Next, identify the factors that may be part of the problem. These may be systems, equipment, materials, external forces, people involved with the problem, and so on.
Try to draw out as many of these as possible. As a starting point, you can use models such as the McKinsey 7S Framework (which offers you Strategy, Structure, Systems, Shared values, Skills, Style and Staff as factors that you can consider) or the 4Ps of Marketing (which offers Product, Place, Price, and Promotion as possible factors).
Brainstorm any other factors that may affect the situation.
Then draw a line off the "spine" of the diagram for each factor, and label each line.
Example:
The manager identifies the following factors, and adds these to his diagram: * Site. * Task. * People. * Equipment. * Control.
Figure 2 – Cause and Effect Analysis Example Step 2
(Click image to view full size.)

Step 3: Identify Possible Causes
Now, for each of the factors you considered in step 2, brainstorm possible causes of the problem that may be related to the factor.
Show these possible causes as shorter lines coming off the "bones" of the diagram. Where a cause is large or complex, then it may be best to break it down into sub-causes. Show these as lines coming off each cause line.
Example:
For each of the factors he identified in step 2, the manager brainstorms possible causes of the problem, and adds these to his diagram, as shown in figure 3.
Figure 3 – Cause and Effect Analysis Example Step 3
(Click image to view full size.)

Step 4: Analyze Your Diagram
By this stage you should have a diagram showing all of the possible causes of the problem that you can think of.
Depending on the complexity and importance of the problem, you can now investigate the most likely causes further. This may involve setting up investigations, carrying out surveys, and so on. These will be designed to test which of these possible causes is actually contributing to the problem.
Example:
The manager has now finished his Cause and Effect Analysis. If he hadn't looked at the problem this way, he might have dealt with it by assuming that people in the branch office were "being difficult."
Instead he thinks that the best approach is to arrange a meeting with the Branch Manager. This would allow him to brief the manager fully on the new strategy, and talk through any problems that she may be experiencing.
Tip:
A useful way to use Cause and Effect Analysis with a team is to write all of the possible causes of the problem down on sticky notes. You can then group similar ones together on the diagram.
This approach is sometimes called CEDAC (Cause and Effect Diagram with Additional Cards) and was developed by Dr. Ryuji Fukuda, a Japanese expert on continuous improvement.
Key Points
Professor Kaoru Ishikawa created Cause & Effect Analysis in the 1960s. The technique uses a diagram-based approach for thinking through all of the possible causes of a problem. This helps you to carry out a thorough analysis of the situation.
There are four steps to using Cause and Effect Analysis. 1. Identify the problem. 2. Work out the major factors involved. 3. Identify possible causes. 4. Analyze your diagram.
Try using Cause and Effect Analysis – you'll find that they are particularly useful when you're trying to solve complicated problems.

Cause-and-Effect Diagram
What is it?
A Cause-and-Effect Diagram (also known as a "Fishbone Diagram") is a graphical technique for grouping people's ideas about the causes of a problem.
Who uses it?
The team, the users, the manager.
Why use it?
Using a Cause-and-Effect Diagram forces the team to consider the complexity of the problem and to take an objective look at all the contributing factors. It helps the team to determine both the primary and the secondary causes of a problem and is helpful for organizing the ideas generated from a brainstorming session.
When to use it?
It is used after the causes have been grouped by relationships (for example, by using a Causal Table or "Why-Because" Technique). It is a useful diagram for problem analysis. Therefore, a Cause-and-Effect Diagram should be used before deciding how to deal with the problem.
How to use it:
Before constructing the Cause-and-Effect Diagram, you need to analyze the causes. The steps are as follows: 1. Re-examine the problem by asking: * What is the problem? * Who is affected? * When does it occur? * Where does it occur? 2. Brainstorm the team's ideas about the causes of a problem using the Causal Table or "Why-Because" Technique. 3. The list of causes should be grouped by relationships or common factors using an affinity technique. 4. You can now illustrate graphically the causes grouped by relationships by using a Cause-and-Effect Diagram where: * The problem under investigation is described in a box at the head of the diagram. * A long spine with an arrow pointing towards the head forms the backbone of the "fish." The direction of the arrow indicates that the items that feed into the spine might cause the problem described in the head. * A few large bones feed into the spine. These large bones represent the main categories of potential causes of the problem. Again, the arrows represent the direction of the action; the items on the larger bones are thought to cause the problem in the head. * The smaller bones represent deeper causes of the larger bones they are attached to. Each bone is a link in a Cause-and-Effect chain that leads from the deepest causes to the targeted problem.

It is difficult if not impossible to solve complicated problems without considering many factors and the cause-and-effect relationships between those factors. Defining and displaying those relationships helps. The first such cause-and-effect diagram was used by Kaoru Ishikawa in 1943 to explain to a group of engineers at the Kawasaki Steel Works how various work factors could be sorted and related. In recognition of this, these diagrams sometimes are called Ishikawa diagrams. They are also called fishbone diagrams, because they look something like fish skeletons.
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What can it do for you?
Quality problems are typically not simple. They often involve the complex interaction of several causes. A cause-and-effect diagram will help you:
• Define and display the major causes, sub-causes and root causes that influence a process or a characteristic.
• Provide a focus for discussion and consensus.
• Visualize the possible relationships between causes which may be creating problems or defects.

Cause-and-effect diagrams are particularly useful in the measure and improve phases of Lean Six Sigma methodology.

How do you do it?
1. Decide which quality characteristic, outcome or effect you want to examine. You might consider Pareto analysis to help you focus on the most important issue.
2. Write your chosen effect on the right side of a paper, board or flipchart and draw a box around it. If you think of this as a fishbone diagram, this is the fish's head.
3. Draw a straight line to the left, the fish's backbone.
4. For each primary cause or category of causes, draw a diagonal line slanting from left to the centerline. Alternate these ribs on the top and bottom of the backbone. Label the end of each rib and draw a box around the label.
5. Draw a horizontal line intersecting the appropriate diagonal line and label it to describe each secondary cause that influences a primary cause. Alternate these medium sized bones to the left and right of each rib.
6. In a similar way, draw and label diagonal lines for third level or root causes, small bones, intersecting the secondary cause lines, medium sized bones.
7. Examine the diagram. If certain causes seem to have a significant effect on the characteristic you are examining, mark them in a special way.

Variation 1: Cause Enumeration
Sometime it may be very difficult to determine the primary causes to be included in your diagram. If that is the case, after you have determined the characteristic or effect you are examining, follow these steps:
• Use brainstorming to create a list of all the possible causes. The list will contain a mixture of primary, secondary and tertiary (or big bone, middle sized bone and small bone) causes.
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• Sort the list by grouping causes that are related.
• Identify or name each major grouping and make your cause-and-effect diagram.
• Machine, Manpower, Material, Measurement, Method and Environment are frequently used major causes that can apply to many processes.

The advantage of the cause enumeration technique is that you stand a much better chance that all causes will be listed, especially hidden ones, and your diagram will be a complete and useful picture. The disadvantage is that it may be difficult to relate all the causes clearly to the result, making the diagram hard to draw.

Variation 2: Process Classification
Sometimes it is more helpful to look at causes in the sequence in which they occur instead of considering overreaching logical categories. With this approach, the center line or backbone follows the sequence of the process.
• Instead of primary causes as the ribs, show the major process steps from left to right.
• Construct your cause-and-effect diagram as before.

The advantage of this technique is that, since it follows the sequence of the process, it will be easy for everyone to understand. The disadvantages are that similar causes will appear again and again, and causes due to a combination of factors will be difficult to show.

Hints for Making Good Diagrams
1. Get input from many people involved in the process. Not only will this make for a more accurate diagram, everyone taking part will gain new knowledge.
2. Make one cause-and-effect diagram for each Critical-To-Quality (CTQ) characteristic you are considering. Trying to include all CTQs on one diagram will make it too large and complicated to be of much use as a problem solving tool.
3. Avoid generalities. Express each cause as concretely as possible.
4. Since you will use your diagram to direct the examination of specific cause-and-effect relationships with data, the characteristic you are considering and all the causal factors should be measurable. If they are not, try to make them measurable or find substitutes.
5. The objective of the cause-and-effect diagram is action. Be sure your causes are broken down to the level at which they can be acted on.

Now what?
• Use your diagram to develop a common understanding of the factors potentially influencing or causing a quality problem.
• Use your diagram as a road map for collecting data to verify the causal relationship of various factors to the characteristic.
• Continue to annotate and modify your diagram as you verify relationships and learn more.

Using a cause-and-effect diagram this way will help you to see which factors in your process need to be checked, modified or eliminated.