Cause and Effect Analysis: Using Fishbone Diagram and 5 Whys

Cause and effect is a relationship between events or things, where one is the result of the other or others. This is a combination of action and reaction. A cause-and-effect analysis generates and sorts hypotheses about possible causes of problems within a process by asking participants to list all of the possible causes and effects for the identified problem.

What is a Fishbone Diagram?

Cause and effect analysis is often conducted by drawing cause-and-effect diagrams (also known as Fishbone Diagram), which organize a large amount of information by showing links between events and their potential or actual causes and provide a means of generating ideas about why the problem is occurring and possible effects of that cause.

The cause-and-effect analysis allows problem solvers to broaden their thinking and look at the overall picture of a problem. Cause-and-effect diagrams can reflect either cause that blocks the way to the desired state or helpful factors needed to reach the desired state.

Fishbone Diagram (also known as Cause and Effect Diagram or Ishikawa Diagram) It visually displays multiple causes for a problem and helps us to identify stakeholder ideas about the causes of problems which Allows us to immediately categorize ideas into themes for analysis or further data gathering. People often use the 5-whys technique in conjunction with the fishbone diagram.

When to Use a Fishbone Diagram?

A cause-and-effect analysis stimulates and broadens thinking about potential or real causes and facilitates further examination of individual causes. Because everyone’s ideas can find a place on the diagram, a cause-and-effect analysis helps to generate consensus about causes. It can help to focus attention on the process where a problem is occurring and to allow for constructive use of facts revealed by reported events.

• When identifying possible causes for a problem
• When having difficulty understanding contributing factors or causes of a system failure
• Most helpful as a team process for brainstorming collaboratively

Steps for Creating a Fishbone Diagram

1. Identify the problem statement (also referred to as the effect).
2. Written at the mouth of the fish
3. Identify the major categories of causes of the problem
4. Written as branches from the main arrow for each of the major categories include: equipment or supply factors, environmental factors, rules/policy/procedure factors, and people/staff factors
5. Brainstorm all the possible causes of the problem
6. Ask “why does this happen?”
7. Write it as a branch from the appropriate category
8. Repeat the other categories by asking “Why does this happen?” about each cause
9. Write sub-causes branching off the cause branches
10. Ask “Why?” and generate deeper levels of causes and continue organizing them under related causes or categories

Use 5 Whys in Combination with Fishbone Diagram

The 5 Whys can be used individually or as a part of the fishbone (also known as the cause and effect or Ishikawa) diagram. The fishbone diagram helps you explore all potential or real causes that result in a single defect or failure. Once all inputs are established on the fishbone, you can use the 5 Whys technique to drill down to the root causes.

For example:

Statement – Your car stops in the middle of the road. 

1. Why did your car stop?

• Because it ran out of gas.

2. Why did it run out of gas?

• Because I didn’t buy any gas on my way to work.

3. Why didn’t you buy any gas this morning?

• Because I didn’t have any money.

4. Why didn’t you have any money?

• Because I lost it all last night in a poker game.

5. Why did you lose your money in last night’s poker game?

• Because I’m not very good at “bluffing” when I don’t have a good hand.

As you can see, in both examples the final Why leads the team to a statement (root cause) that the team can take action upon. It is much quicker to come up with a system that keeps the sales director updated on recent sales or teach a person to “bluff” a hand than it is to try to directly solve the stated problems above without further investigation.