What does the evidence actually tell us?

1
What does the evidence actually tell us?

• Evaluating Headlines

2
Hang-gliding or horse-riding?

• The data
• In 1985, 15 people died in horse-riding
  accidents, compared to one death from
  hang-gliding.
• Is the headline reasonable?
• What else might you need to know to make a
  judgement?

• Hang-gliding is safer than horse-riding to
  judge by a new survey of sports deaths.
• The Times,
• 12 March 1987

3
Horse-riding or motor-cycling?

• The data
• In 2007, it was reported that you could expect a
  serious motorbike accident every 7000 hours,
  compared to a serious riding accident every 350
  hours.
• Is the headline reasonable?
• What else might you need to know to make a
  judgement?

• riding has now overtaken motorcycling as the
  biggest cause of rural casualties
• The BBC
• 23 March 2007

4
Comparing risks

• 1 micromort is defined as a 1 in a million chance
  of dying
• 1 million micromorts is a mort, and means certain
  death.

• In order to compare risks of different
  activities, we need a common currency or unit
  or risk.

5
Comparing risks

• 1 micromort is equivalent to
• 230 miles in a car
• 6000 miles in a train
• 3 flights

• 1 micromort is a 1 in a million chance of dying

6
Comparing risks

• A general anaesthetic in a UK hospital carries a
  risk of 5 micromorts, on average, equivalent to
• riding a motorcycle 30 miles
• riding in a car 1000 miles
• going on one scuba-dive
• living 4 hours as a heroin user
• or serving 4 hours in the UK army in Afghanistan

• 1 micromort is defined as a 1 in a million chance
  of dying
• 1 million micromorts is a mort, and means certain
  death.

7
Comparing risks

• UK service personnel are exposed to an average of
  33 micromorts per day
• equivalent to riding a motorcycle from London to
  Manchester
• of course, front-line troops are exposed to
  considerably greater risks, as this is an average
  figure.

• 1 micromort is defined as a 1 in a million chance
  of dying
• 1 million micromorts is a mort, and means certain
  death.

8
Comparing risks

• 1 hang-gliding flight is equivalent to 8
  micromorts.
• 1 ride on a horse is equivalent to half a
  micromort.
• 6 miles on a motorcycle is equivalent to 1
  micromort.

• 1 micromort is a 1 in a million chance of dying

What do you think? Which is most dangerous?
9

• What do you make of these headlines now?