Conditional Probability

jeffhewins

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Oct 23, 2005
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Having troubles with this probability question. Can one one help?

Suppose that 20% of all inspected trucks have problems that need to be fixed. Unfortunately, when trucks are inspected they fail to detect these problems 12% of the time. Consider a truck that is inspected and is found to be free of problems. What is the probability that there is indeed something wrong that the inspection has failed to uncover?
I think I can use the Bayes theorem, however, I cant seem to figure out how to get pr(B) in the below formula.

A="a truck is faulty"
B="no fault has been detected"

and Bayes theorem tells us

pr(A|B) = pr(A).pr(B|A)/pr(B)

And Idea?
Thanks Jeff
 
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