STAT 100A Lecture Notes - Lecture 16: Random Variable, Electronic Component
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De nition n is to be chosen randomly and without replacement from a population of n , of which m possess a particular characteristic, and the other n m do not. If x is the number of individuals in the selected sample, then x is said to be a hypergeometric random variable. P(x = i) = (cid:2)n i(cid:3)(cid:2)n m n i(cid:3) (cid:2)n n(cid:3) A buyer of electrical component buys electrical components in lots of size 10. It is his policy to inspect 3 components randomly from a lot, and to accept the lot only if all 3 are non-defective. If 30% of the lots have 4 defective components and 70% of the lots have 1 defective components, what is the proportion of the lots that the purchaser rejects. Let a be the event that the buyer accepts the lot. P(a) = p(4 defective) p(a|4 defective) + p(1 defective) p(a|1 defective)
