[chbot] Is there a statistician in the house?
Stephen Irons
stephen at irons.nz
Sun Oct 18 05:57:21 BST 2020
I seem to remember doing calculations like this a long time ago...there
are a number of variations which are probably all related. I have not
been able to find any Google search terms that give me anything useful.
A factory produces a batch of 10_000 units.
I test 100 units; there are 3 failures. What failure rate can I expect
from the whole batch? What is my confidence in that estimate?I test 100
units; there are 0 failures. What failure rate can I expect from the
whole batch? What is my confidence in that estimate?How many units do I
need to test to have 99% confidence that there will be less than 1%
failure rate from the whole batch?
Can someone tell me what you call this type of calculation? Point me to
a suitable reference site?
All of the examples I find online are of the form: a factory produces
widgets with x% failure rate; out of a sample of y units, what is the
probability of finding z defective units...this is probably the same
calculation from the other direction.
This is just for interest. In my specific case, I had 36 failures out
of a sample of 50 taken from a batch of a few thousand -- this is
clearly not acceptable. But we now have a repeatable test that causes
the failure.
Stephen Irons
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