Accident Investigation

Resources - Accident Investigation and Root Cause Analysis

The Five Whys Technique

The 5 Whys technique is a simpler form of fault tree analysis for investigations, especially investigations of specific accidents as opposed to chronic problems.

The 5 Whys technique is a brainstorming technique that identifies root causes of accidents by asking why events occurred or conditions existed.

The 5 Whys process involves selecting one event associated with an accident and asking why this event occurred. This produces the most direct cause of the event. For each of these subevents or causes, ask why it occurred. Repeat the process for the other events associated with the accident.

Limitations of the 5 Whys technique

The 5 Whys technique is an effective tool for determining causal factors and identifying root causes. However, it does have three primary limitations:

  1. Brainstorming is time consuming. Compared to other techniques, the 5 Whys technique can be time consuming. The brainstorming process can be tedious for team members trying to reach consensus. This is especially true for large teams.
  2. Results are not reproducible or consistent. Another team analyzing the same issue may reach a different solution. The brainstorming process is very difficult, if not impossible, to duplicate.
  3. Root causes may not be identified. Like event and causal factor charting, the 5 Whys technique does not provide a means to ensure that root causes have been identified.

Source: USCG Risk-based Decision-making (RBDM) Guidelines.

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