On Mon, 17 Apr 2006 11:35:04 UTC, Ronald Raygun
wrote:

: Ian Johnston wrote:
:
: About 3000 people in the UK die in road accidents each year. Assuming
: that almost all the population uses roads in some way, that;s 3000 out
: of 60 million, which is 1 in 20000.
:
: If the average person lives to the age of 80, it follows that 1 in 80
: of the population dies each year anyway (from all causes). Thus you'd
: expect 1 in 700000 of the population to die in any hour.

You'd expect that anyway, from the average lifespan being about
700,000 hours. But maybe that's what you meant?

: If the average person spends 200 hours a year on the roads, you'd expect
: 1 in 3500 of the population to die on the roads each year (from all causes).

You are assuming, though, that "being on the road" and "being likely
to die of natural causes" are independent, which is quite definitely
not the case. In addition, the 3,500 deaths per year does not, as far
as I am aware, count people who have heart attacks on buses and so on
- it's people who dies as a result of road accidents.

: If in addition 1 in 20000 die from road accidents per year, this suggests
: 6 in 7 of all road deaths are non-accidental.

.... and, as per above, not counted in the 3500.

: Of the 5000 or so glider pilopts
: in the UK, about 5 die flying annually which gives a death rate per
: annum of 1 in 1000.
:
: You'd still expect 1 in 700k gliders to die each hour simply because they
: are part of the general population.

Neither "being a glider pilot" nor "dying of natural causes" are
evenly distributed, and they are not independent. Would you expect 1
in 700,000 of both schoolchildren and octogenerians to die every hour?

: Doesn't that make gliding 30 times as dangerous as being on the road?

It's certainly a lot more dangerous, but I don't think your
statistical approach demonstrates how much more dangerous.

Ian