Lecture 11 - Tools and Techniques Used in Incident Investigation

Question 1

What is the 5-Why analysis?

Answer 1

REFER TO SLIDES

Question 2

What are some criticisms on 5 Why analysis?

Answer 2

• For complex incidents 5 whys may not be sufficient, some causal chains may require more, some less
• Quality depends on investigator’s knowledge
• Different results for different investigators
• Tendency to isolate a single root cause

Question 3

What is the cause and effect (fishbone) diagram?

Answer 3

REFER TO SLIDES

Question 4

What are some criticisms on cause and effect diagram?

Answer 4

• Fails to make the distinction between necessary conditions and sufficient conditions
• Early grouping in categories hinders linking causes from different categories
• Quality depends on investigator’s knowledge

Question 5

What is fault tree analysis?

Answer 5

• Uses logical pathways to connect underlying causes to higher level causes
• Causes connecting through an AND gate are collectively necessary and sufficient to produce the
  higher level cause
• Causes connecting through an OR gate to a higher level event are individually sufficient
  REFER TO SLIDES

Question 6

What are some criticisms on fault tree analysis?

Answer 6

• Time- and resource-consuming (when used for complex accidents)
• Does not allow interactions between different branches of the tree
• Only includes faults (and some versions also errors), not context
• Difficult to include information regarding timing and duration
• Quality depends on investigators’ knowledge

Question 7

What is cause tree analysis?

Answer 7

• Derived from and very similar to Fault Tree Analysis
• Allows inclusion of situational factors that contributed but are not necessarily faults or failures
• Mainly used retrospective, no probability calculations needed
• Most versions only use AND gates, if complete information is available regarding factors involved (so no need to include potential alternative causes), i.e. all underlying factors are necessary and together sufficient to lead to higher level cause
  REFER TO SLIDES

Question 8

What is Sequentially Timed Event Plotting

Answer 8

• # Identify the main events/A STEP worksheet structures the analysis:Actors involved in the incident are listed down the vertical axis
  A timeline is established on the horizontal axis
  ==
• # Actions that contributed to the accident to construct event building blocks which contain the following information:the time at which the event/action started;
  the duration of the event/action;
  the agent which caused the event or action;
  the description of the event/action, and,
  the name of the source which offered this information.
  ===
• Interconnect the events/actions with arrows

Question 9

What are some criticisms on Sequentially Timed Event Plotting?

Answer 9

• Difficult to represent human factors issues and organisational factors that influenced events
• Time- and resource-consuming (when used for complex accidents)

Question 10

What is TapRoot?

Answer 10

The TapRooT technique includes:
- Snapchart – a visual technique for collecting and organizing information about events, sequence, and details/conditions surrounding events, to understand what happened, like an event time sequence with additional information for some events
- Root cause tree – a systematic, repeatable way to find the root causes of human performance and equipment problems (aka causal factors) identified in the snapchart — the root cause tree helps investigators see beyond their current knowledge
- Corrective action helper – helps investigators develop effective corrective actions
===
- TapRooT defines a root cause as ‘the absence of a best practice or the failure to apply knowledge that would have prevented the problem’
- TapRooT defines root cause analysis as ‘the search for the best practices and/or the missing knowledge that will keep a problem from recurring’
- With this positive spin on the purpose of doing a root cause analysis, along with its strong focus on human factors underlying errors, it helps to steer away from assigning blame

Question 11

What are some criticisms on TapRoot?

Answer 11

• Investigators will not find factors that are not included in the root cause tree (although developers insist it is more than a mere checklist, with questions guiding users to areas of the tree)
• Up to user to decide which events and/or surrounding conditions are causal factors that need further investigation – so quality still depends on investigator (some guidance provided)
• Protected by copyright; not available in public domain, need to attend (and pay) for training course