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S2 Module Question watch

1. Hi there!!

I don't understand part b in problem 3 in section 1E.

Can someone please explain? It just nags me that i don't get it!!

Thankx!!!
2. ...? What's the question?
3. Hi , how are you? Stephen

I have posted the question in two scans. Part b , the expecation part is what I don't get? If you could explain the reasoning in detail.

thanx

dave
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4. Let the no. of defectives is X~B(10, 0.01).

if X=1 then you're going to end up sampling 20 items,
if X is not equal to 1 then you just need the initial sample of 10 items (to decide whether to accept/reject the batch).

So Expected number of items sampled = 20*P(X=1) + 10*[1 - P(X=1)]

5. Big Thanx to benevolent member!!!

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