stat1301testsol

stat1301testsol - 10/11 THE UNIVERSITY OF HONG KONG...

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10/11 p. 1 THE UNIVERSITY OF HONG KONG DEPARTMENT OF STATISTICS AND ACTUARIAL SCIENCE STAT1301 Probability and Statistics I Class Test Solution October 25, 2010 1. [10 marks] Two different suppliers, A and B, provide the manufacturer with the same part. All supplies of this part are kept in a large bin. In the past, 2% of all parts supplied by A and 4% of parts supplies by B have been defective. Moreover, A supplies three times as many parts as B. (a) Suppose that you reach into the bin and randomly pick a part. Find the probability that this part is defective. Ans: () ( ) ( ) ( ) ( ) 025 . 0 25 . 0 04 . 0 75 . 0 02 . 0 | | = × + × = + = B P B defective P A P A defective P defective P (b) Suppose that you reach into the bin, randomly pick a part and find it non -defective. What is the probability that it was supplied by B? Ans: ( ) ( ) 2462 . 0 = 025 . 0 1 25 . 0 04 . 0 1 | | × = = defective P B P B defective P defective B P P. T. O.

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10/11 p. 2 2. [15 marks] On the basis of past experience, the car agency estimates that in next year the number of potential buyers of Benz will be distributed as ( ) 4 . 0 , 10 b .
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stat1301testsol - 10/11 THE UNIVERSITY OF HONG KONG...

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