quality asurance problem....
- From: Davide Falessi <d.falessi@xxxxxxxxx>
- Date: Fri, 25 Apr 2008 02:06:50 -0700 (PDT)
I have a set of 10000 elements to buy; I want to do some quality
assurance activity in order to avoid to buy invalid elements. I cannot
check all the elements by eye because it would require too much
effort; hence I’d like to prioritize the elements to focus my effort
on the most urgent elements to check. I have an automatic test that
provides the probability of correctness of an element; moreover I know
that the test gives a 20% of false positive and a 30 % of false
negative.
1)Suppose that I have an element of which the test estimate a
probability of correctness of 75%; which is the posterior
probability?
I’m afraid I’m unable to apply the Bayesian theorem because I do not
know the number of correct elements. My instinct tells me to count the
frequency in the past in which an element was really correct when the
estimated probability by the tool was less or equal then 75%; suppose
that such frequency is 50%. Consequently, my instinct will say that an
element of which the test estimate a probability of correctness of 75%
has a posterior probability to be correct of 50%. Am I right???
2) Suppose that I cannot check all the elements by eye but I need to
use the automatic test to prioritize the elements to check by eye;
suppose that I run the automatic test on all the elements and then I
order the elements according to the probability of correctness
provided by such a test; suppose that I’ve analyzed all the elements
(in case the 43%) with a probability (provided by the test) of
correctness lower than 65%;
How to calculate the actual quality of the entire set of elements? Is
is the probability that there is an incorrect elements in the
remaining (57%) ones (i.e. the ones with a probability of correctness
higher than 70%)??? How to do that?
Please help me!
.
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