With causal analysis, we uncover the events that caused a problem to find its root cause. A clear understanding of the events leading to an incident helps to find its root cause. A causal effect chart describes the events leading to an incident and the associated conditions. How do you create this chart? Let’s see the steps for building a causal factor chart.
A causal factor chart starts with the result
The first piece to construct a causal factor chart is the end of the story. We work backward to build this chart. Therefore, the starting point of the chart is the loss event or condition.
Starting with the loss event at the left, work backward, adding the events that led to the last one you add. Add these building blocks following time and logic sequence. The sequence of events leading to the incident runs from left to right in the center of the chart. These events are the primary events.
The events and conditions that led to each primary event are the secondary events. They are the reason why the events on the centerline happen. The secondary events are drawn above the main event line. Less significant events go below the main event line. These events provide additional details but do not represent possible causes for the loss event.
Steps to build the Causal Factor Chart
- Draw a rectangular block with the loss event, problem, or accident.
- The first primary event is what happened right before the incident.
- Verify the information you have regarding this event by asking several questions. Use 5W1H (why, who, when, where, and how) to formulate those questions.
- Gather data to answer the questions developed in the previous step and use it to find the sequence of occurrences that lead to the primary event. These are the secondary events.
- Look for those states or conditions that facilitate the occurrence of an event and them to the chart.
- Go to primary event on top of this sequence and repeat steps 2 to 5.
- Keep repeating these steps until the sequence is deemed complete.
- Review the sequence and ask if it explains why the loss event happened. Collect more information and add or edit blocks if needed.
- Identify the causal factors.
Building a causal factor chart is just the first step
Below you can see an example of how the causal factor chart looks. This chart helps identify the causal factors that lead to an incident. However, it is not for simple situations where the timeline is not critical.
Knowing the causal factors does not necessarily mean that you learn the root cause. Further analysis using a cause and effect diagram or 5 Why may be necessary.