The Norm Chronicles (42 page)

Probability sounds sensible enough, but whenever you reach for a firm and meaningful definition the concept loses shape – although it is a number, show us the scales or stick that you can measure it with. Egyptians, Greeks, Babylonians and others did amazing things with algebra, geometry, number theory and much more, but they never even got started on probability, and the omission is telling. DS says he has spent many years trying to work out why people find probability intuitively difficult and confusing. He has concluded that it is because probability is intuitively difficult and confusing. MB adds that he has often reported people’s communication of risk and found the communicators don’t really know what they are communicating. Just when anxious people most want clarity, they find muddle. There is a reason for that. It
is
a muddle. Norm, sadly, could never work that out.

The view that probability doesn’t exist is unusual but moderately respectable.
¹
It is also liberating, as it means that we are free to use a variety of metaphors and analogies when talking about risk, chance or probability, free to look at it from multiple perspectives and accept that perspective matters.

For example, a 12 per cent risk of a heart attack is often communicated as ‘out of 100 men like you, in 10 years we expect 12 to have a heart attack or stroke’. But there are not 100 men like you, and the probability is not yours. A more gripping metaphor might be to say ‘of 100 ways that things may turn out for you over the next 10 years, in 12 of them you will have a heart attack or stroke.
*

So, which of the 100 are you this time? And when Prudence wonders if she is the one in 100 and says ‘What if …?’, has she a point? Or when Norm says she exaggerates, doesn’t he have one too? And when Kelvin says ‘so what?’, is he wrong?

Perhaps you have made your peace with the dual nature of risk, chance and probability, and you are comfortable with its elusiveness from a personal point of view. But if Norm, Prudence and Kelvin are not wrong to say what they say – each different, each to their own view of risk – then which is the right number for them? On the other hand, if you do happen to look up and see a falling piano …

Figure 36:
The authors’ calculations of MicroMorts per hazard

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Figure 37:
Average MicroLives (1/2 hour of life-expectancy) lost or gained per day of exposure to a specified hazard ratio for all-cause mortality, averaged over life after 35

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