Miata Mailing List: July 1993, Message #136
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   From: colburn@cis.uab.edu (Gordon A. Colburn)
Subject: Rollbars & rollovers
   Date: Thu, 15 Jul 1993 10:05:08 -0400


Ken Buck writes:

> something else to consider is that over time, the odds multiply.
> so over a period of 10 years of driving, the chances of getting:
> (a) involved in accident: 10 * .04 = .40 (2 in 5)
> (b) involved in rollover: 10 * .0008  = .008 (1 in 125)
> (c) killed in rollover:   10 * .000056 = .00056 (1 in 1785)
> something to think about.

I beleive this is incorrect. For instance, if we have a period
of 100 years of driving, Ken's argument would give us a chance
of 4 (400%) of being involved in an accident! I believe it
should be:

a) 1 - .96 ^ 10 = .335 (1 in 3)
b) 1 - .9992 ^ 10 = .008 (1 in 125)
c) 1 - .999944 ^ 10 = .00056 (1 in 1785)

so Kenneth's math works out (by accident) for all cases but a.
But if we expand the period of time, Kenneth's method will
begin to show considerable error.

> personally, i think the risks are low enough for me

I agree! One of the Miata's principle virtues is simplicity.