7. 0.1210.24 points ! Previous Answers DevoreStat93.E512 My Notes Ask Your Teach

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7. 0.1210.24 points ! Previous Answers DevoreStat93.E512 My Notes Ask Your Teacher Suppose that only 0.1% of all computers of a certain type experience CPU failure during the warranty period. Consider a sample of 9,000 computers. (a) What are the expected value and standard deviation of the number of computers in the sample that have the defect? (Round your standard deviation to two decimal places.) expected value standard deviation 3 (b) What is the (approximate) probability that more than 9 sampled computers have the defect? (Round your answer to three decimal places.) computers computers (c) What is the (approximate) probability that no sampled computers have the defect? (Round your answer to five decimal places.) You may need to use the appropriate table in the Appendix of Tables to answer this question. Need Help?Read It Talk to a Tutor

Explanation / Answer

a)
expected value = mean = 9000 * 0.001 = 9
std. dev. = sqrt(0.001*0.999*9000) = 3

b)
P(X > 9) = P(z > (9 - 9)/3)
= P(z > 0)
= 0.5

c)
P(X = 0) = (1 - 0.001)^9000 = 0.00012

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