1) The document summarizes a presentation by Roger Kahler on hypothesis forming and testing for incident investigation. 2) It discusses using taxonomy and modeling to analyze collective and individual incident data and form testable hypotheses. 3) Examples are provided of using hypothesis forming and testing to analyze crane fatalities data and an individual incident involving a vehicle accident.

1. New Zealand OHSIG Conference
26-28 October 2011
Hypothesis Forming and Testing
Roger Kahler
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2. Two Applications
1. “Collective” Incident Data
2. An “Individual” Incident
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3. Scientific Process
Interacting Concepts
• Models / Modelling
• Hypothesis forming and testing
• Taxonomy
Can be applied collectively/individually
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4. Taxonomy
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5. Crane Fatalities – A Taxonomic Analysis
Overhead power
Electrical Energy – lines - 214
electrocution - 217
Portable equipment
-3
Falls of Objects -
Crane Fatalities Gravitational 144
1985-1995 Energy - 268
Falls of People - 88
525
Falls of Crane –
overturn - 36
Machine Energy - Person Caught
34 Between - 24
Person Run Over -
10
Other - 6
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6. Taxonomies
• Show relative frequency of levels of Damage
• Show relative importance of different damaging
energies
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7. Incident Time Base
• Damage as a consequence of an Energy Exchange
 Situation stable
 Situation moving out of control
 Situation out of control Time
 DAMAGE
 Recovery
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8. Damage Reduction
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9. Damage Reduction
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10. Hypothesis Forming & Testing
Hypothesis Forming & Testing
as applied to
Individual Incidents
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11. What’s Your Hypothesis?
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12. What Actually Happened
Video available at
http://www.youtube.com/watch?v=LVmpEPdPBk8
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13. An Individual Incident
• What are the roles of
– Taxonomy
– Modelling
– Hypothesis Forming and Testing
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14. Role of Hypothesising in the
Journey of an Investigation
• Scope
• Collect Information Data ← Informally
• Form and test hypotheses ← Formally
• Description
• Analysis and Recommendation
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15. Observers
• Incident Investigators are first and
foremost observers of a situation
• Observations have to first be made
• A frame of reference will improve
the quality and quantity of
observations
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16. Observation
An observation will be:
1. SUPPORTIVE of the hypothesis
2. REJECTING of the hypothesis
3. NOT APPLICABLE to the hypothesis
4. MORE INFORMATION REQUIRED before a decision
can be made as to 1, 2 or 3.
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17. Hypothesis
• At some point a decision has to be made
with respect to the observations
• This involves forming a hypothesis
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18. Possibility and Probability
IMPOSSIBLE - POSSIBLE
PROBABILITY
50% 95% 99%
Balance of 1:20 “Variation due Beyond reasonable
probabilities to chance” doubt
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19. Self Fulfilling Hypothesis
• Hypothesise
• Select evidence to support, not reject
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20. Hypothesis Forming and Testing
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21. Hypothesis Forming and Testing
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22. Hypothesis Forming and Testing
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23. Hypothesis Forming and Testing
Car „A‟
Start of
curve
Double white lines
100 m
2 skid marks 20 m long
grid
HYPOTHESIS: Car „A‟ braked heavily after crossing grid.
Questions: What observations can you make that could be “supportive” or
“rejecting” of this hypothesis?
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24. Hypothesis Forming and Testing
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25. Hypothesis Forming and Testing
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26. Hypothesis Forming and Testing
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27. Hypothesis Forming and Testing
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28. Hypothesis Forming and Testing
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29. Hypothesis Forming and Testing
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30. Hypothesis Forming and Testing
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31. Hypothesis Forming and Testing
How could you formally test an hypothesis?
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32. Hypothesis Forming and Testing
Hypothesis = (testable statement)
“Supporting” “Rejecting”
Comments
Observations Observations
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33. Engaging Experts
Questions to People Investigating Failures
1. What do you think happened? (Hypothesis)
2. Why do you think this? (Supporting information)
3. Any observations that don’t fit? (Rejecting
information)
4. What could be done differently in future?
(Essential factors & potential recommendations)
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34. Case Study – Low Loader Fire
• List supporting and rejecting observations for each
hypothesis
• Decide whether the particular hypothesis is
possible/impossible
• Of the possible hypothesis, assign a probability
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35. The End
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