Salut Alan,
On Sun, 27 Mar 2016 15:52:00 +0100
"Alan Melia" <alan.me...@btinternet.com> wrote:
> I am out of the business now, well retired, so my opinion carries
> little weight,
> :-)) but for whatever it does, my thought is that MTBF is a pretty useless
> parameter in general. This is a relatively low volume unit manufactured by a
> variety of different firms with each their opinion on the best optimum.
>
> The statistical base to MTBF is faulty and in my opinion its only use is to
> indicate where a design might be improved by changing the component mix. The
> actual value that falls out of the end of the calculation for a desgn is
> completely meaningless, but the non-tech bean-counters wanted a way to
> justify more expensive designs, and the purchase of expensive kit.
Yes, the MTBF is a very simplicistic measure and there are a couple
of assumptions in its calculation which do not hold generally (or
rather, it's rather seldom that they hold). Yet it gives a number to
something that is otherwise relatively hard to measure and the number,
even though flawed, makes it possible to compare different devices
on their reliability. As this is more a rule of thumb comparison,
you shouldn't read too much into a 10% difference. Yet a 100% difference
is significant, no matter which of the assumptions do not hold.
I my case here, I use the MTBF as a stand in for a more general reliability
probability density function, a term which might confuse more than clarify
in the question asked.
Attila Kinali
Attila Kinali
--
Reading can seriously damage your ignorance.
-- unknown
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