NEBOSH Incident Investigation

Question 1

What does Heinrich's domino theory of accident causation propose?

Accepted Answer

Accidents result from a chain of sequential factors (social environment, fault of person, unsafe act/condition, accident, injury) and removing one 'domino' can prevent the injury

Answer

Accidents are purely random events that cannot be predicted

Answer

All accidents are caused by equipment failure alone

Answer

Accidents only occur when multiple workers are present

Question 2

What is the 'Swiss cheese' model of accident causation?

Accepted Answer

Reason's model showing that accidents occur when hazards pass through aligned holes (weaknesses) in multiple defensive layers — each layer has gaps, and an accident happens when the gaps line up

Answer

A model showing that Swiss workplaces are safer than others

Answer

A model based on the shape of workplace floor plans

Answer

A theory that accidents are caused by food contamination

Question 3

What is the '5 Whys' technique used for in incident investigation?

Accepted Answer

Repeatedly asking 'why' to drill down through symptom-level causes to identify the root cause of an incident

Answer

Asking five different witnesses about what happened

Answer

Identifying five possible preventive measures

Answer

Checking five different regulatory requirements

Question 4

Under RIDDOR 2013, which of the following events must be reported to the relevant enforcing authority?

Accepted Answer

A fracture of any bone other than fingers, thumbs, or toes suffered by a worker as a result of a work-related accident

Answer

Any minor cut or bruise requiring a plaster

Answer

A worker taking a single day off due to a headache

Answer

A near-miss that no one witnessed

Question 5

What is a fishbone (Ishikawa) diagram used for in root cause analysis?

Accepted Answer

To visually organise potential causes of an incident into categories (such as People, Methods, Materials, Machinery, Environment, Management) to systematically identify root causes

Answer

To map the layout of a workplace

Answer

To track the timeline of events leading to an accident

Answer

To calculate the financial cost of an incident

Question 6

Why is near-miss reporting considered important in incident investigation and prevention?

Accepted Answer

Near-misses share the same root causes as actual incidents — investigating them provides an opportunity to identify and fix hazards before someone is actually harmed

Answer

Near-misses are legally required to be investigated under RIDDOR

Answer

Near-miss reports are only important for insurance purposes

Answer

Near-misses only need to be recorded, not investigated