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    Hey im doing a past paper and i couldnt answer question 7 part 3 http://www.ocr.org.uk/download/pp_09...ce_4732_01.pdf

    The part about 4 batches being slescted. The answer to P(X=3) is 0.0853 and P(Xgreater or equal to) is 0.718 Thanks.

    Let Y=no. of batches that contain at least one second. So Y=0,1,2,3,4.
    Since prob(a batch contains at least one second)= 0.718 then Y~B(4, 0.718).
    So you want P(Y<3).
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Updated: April 6, 2011

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