To find and understand the causes and not be stuck with the symptoms.
What is it?
It is a graphic representation that relates an EFFECT (Problem, Symptom), Characteristic of the Quality or Subject under study), with all the possible CAUSES or factors that generate it.
It was developed in 1953 by Professor Kaoru Ishikawa in Tokyo. It is also known as the Ishikawa Diagram, the Activity-Results Tree, or, more commonly, the Fishbone Diagram, due to its resemblance to the backbone of a fish.
Why use it?
It is a very useful tool for a team to identify and graphically display all the possible CAUSES related to a previously chosen EFFECT.
Finding cause-and-effect relationships can be useful when trying to solve a problem, but also when trying to understand the relationships between activities and outcomes. That is, which activities will produce certain outcomes. And vice versa.
If used for problem solving allows us to think about all the possible causes that could have generated it.
What benefits does it have?
Build a snapshot of group knowledge and consensus around the topic under study. This creates support and commitment for the resulting solutions.
It allows the team to focus on the problem itself, not on blaming others, the history of the problem, or the personal interests of team members.
Seeks to have the team focus on causes, not symptoms.
Subdivide the causes into their main parts and show how these interact with each other.
The difference with Brainstorming is that Fishbone Thinking is a Parallel Thinking technique. This means that it presupposes knowledge of the main variables related to the problem. When thinking about possible causes, they will be related to each of the intervening variables.
How is it done?
1. Choose a single topic to study.
Find all the objective data for that chosen symptom, problem, or characteristic. To do this, use indicators with statistics, checklists, on-site observations, etc.
Include all relevant information. The “What,” “Where,” “When,” “Who,” and “How Much” of the problem, as we saw in the tool. The Magic Questions: 5W2H.
To specify the problem use only data, not opinions.
2. Objectively define the EFFECT, symptom or problem.
Ensure that the entire team agrees on the problem statement.
3. Select the most appropriate categories. That is, the variables most closely related to the topic under study. This is essential for successful execution of the exercise.
Although they are commonly used 6M = Materials, Machines, Methods, Measurements, Mother Earth and People, it is key that those who make up the team master the subject under study in order to decide if that categorization is correct or another should be used.
For example:
- 4S: Suppliers, Skills, Systems, Surroundings
- 4P: Places, Procedures, People, Policies
- PQCDSM: Productivity, Quality, Costs, Delivery, Safety and Health, Morale (Satisfaction)
- 5S: Client Satisfaction, Employee (Employees), Shareholders (Shareholders), Suppliers (Suppliers), Social (Community), Global (Environment)
- 6V: Technical, Economic, Ecological, Political, Security, Continuity Viability.
4. Construct the Cause and Effect / Ishikawa Diagram following these steps:
a. Place the definition of the topic to be studied in a box on the right side of the surface. Where it says EFFECT. (See graphic)
b. Write down the chosen categories. Keep in mind that there is no single or perfect set; find the ones that best fit the problem under study. That is, the 6Ms don't always best reflect the probable causes. Everything will depend on the issue being analyzed.
c. Imagine all the causes that led to the EFFECT.
To do this, use the Check Sheets with the data collected by team members before the meeting, Indicators, On-site Observations, etc.
Through brainstorming, each of the potential causes is linked to the variables at play (6M or whatever). Follow the recommendations we saw in the article. Brainstorming.
d. Place the identified probable causes in the appropriate category. Some causes may fit into more than one category. Choose the most representative one.
e. From a chart construction perspective, it is recommended to use Post-it notes as they allow for faster work.
f. If ideas emerge slowly, use categories as triggers, for example: What aspect of “materials” is causing…?
g. For each of the probable causes, you should ask because successively until reaching what is believed to be the root cause.
h. Since the diagram is a visual representation of all causes possible, it is now a matter of investigating the validity of each of them by seeking objective information that demonstrates them.
i. Causes must continue to be opened up to the level at which they can be acted upon, otherwise their identification will be a pointless exercise. This is done by repeating the question because as many times as necessary.
Plan of action
Once the causes have been verified, a list should be prepared in order of their level of impact on the EFFECT and, if it is a Problem Analysis, an Action Plan with countermeasures should be prepared.
Remember that the Ishikawa Diagram can be used for other purposes, such as understanding which Activities generate certain Results in order to prepare the Indicator Tree. In this case, once these relationships have been verified, the relationship between the indicators can be constructed.
Conclusion
In itself, the Fishbone diagram is merely a representation of the groupthink process. To be effective, each of these possible causes must be validated with objective data from Observed Phenomena (Genjitsu), with Predefined Standards (Gensoku or basic rules), and subsequently endorsed with the Principles and Laws in play (Genri).
It must be remembered that if we use it for problem solving, we are not looking for potential causes (as the FMEA dynamic does – Failure Mode and Effects Analysis) but for current causes, which are occurring or have occurred, and which for that very reason generate the undesired effect that we are trying to eliminate.
The Cause-Effect Diagram is a very useful way to apply parallel thinking techniques to the search for solutions.
