What is a cause-effect graph?
A cause-effect graph is a technique used in black-box testing.
In black-box testing, testers are concerned with the inputs and corresponding outputs of a system only. They do not need to know the underlying code.
The cause-effect graph was created by Kaoru Ishikawa and thus, is known as the Ishikawa diagram. It is also known as the ‘fish-bone’ diagram because of the way it is structured. A cause-effect graph shows the relationship between an outcome (effect) and the factors (causes) that lead to it.
The illustration below shows a cause-effect graph:
Why do we use a cause-effect graph?
A cause-effect graph is primarily used to identify factors that lead to an outcome. We can list the reasons for using a cause-effect graph as below:
- Identify reasons or causes for a problem or outcome.
- Analyze existing issues.
- To understand the interaction of a system.
How to create a cause-effect graph
A cause-effect graph can be created by following the steps below:
- Identify the outcome.
- Create the effect box along with the spine.
- Identify various causes of the effect.
- Group similar causes into common categories and fill in the boxes.
Benefits of a cause-effect graph
A cause-effect graph has the following benefits:
- It leads to a more structured approach toward identifying the causes of a problem or outcome.
- Easier representation to list different causes of an effect.
- Diagram is intuitive and easy to understand.
- Highlights areas where further data collection is required for analysis.
- Motivates a team by presenting ideas visible to all for collaborative study.
Example
The illustration below gives an example of a cause-effect graph used in a software:
We assume that a database issue has occurred within the software.
The illustration above presents a scenario that shows different factors responsible for database failure in a software. These scenarios include:
- Storage limitations
- Non-structured data
- Slow access time of the database
- Database not active throughout
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