Question 841135: Suppose that a library has two computer labs. Lab-A contains 50 PC's and Lab-B contains 30 PC's. Nine of the Lab-A PC's and 4 of the Lab-B PC's have been infected with spyware. A sample of PC's will be inspected to check for spyware.
a. Suppose 8 Lab-A PC's are randomly drawn. What is the probability that none of the PC's in the sample is infected?
b. Suppose 8 Lab-B PC's are randomly drawn. What is the probability that none of the PC's in the sample is infected?
c. Suppose 4 Lab-A PC's are randomly drawn, and a separate random sample of 4 Lab-B PC's is drawn. What is the probability that none of the PC's in either sample is infected?
d. Suppose that from a combined list of all 80 Lab-A and Lab-B PC's, 8 PC's are randomly drawn. What is the probability that none of the PC's in this sample is infected?
I think this would be a Hypergeometric distribution but i dont know where to begin. im thinking the sample space will be 80 but im not sure about the others.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Suppose that a library has two computer labs.
Lab-A contains 50 PC's ; Nine are infected
Lab-B contains 30 PC's ; Four are infected
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A sample of PC's will be inspected to check for spyware.
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a. Suppose 8 Lab-A PC's are randomly drawn.
What is the probability that none of the PC's in the sample is infected?
Ans: 41C8/50C8
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b. Suppose 8 Lab-B PC's are randomly drawn. What is the probability that none of the PC's in the sample is infected?
Ans: 26C8/30C8
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c. Suppose 4 Lab-A PC's are randomly drawn, and a separate random sample of 4 Lab-B PC's is drawn. What is the probability that none of the PC's in either sample is infected?
Ans: (41C4/50C4)*(26C4/30C4)
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d. Suppose that from a combined list of all 80 Lab-A and Lab-B PC's, 8 PC's are randomly drawn. What is the probability that none of the PC's in this sample is infected?
Ans: 67C8/80C8
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Cheers,
Stan H.
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