CEE5970_Midterm-Soln2010

# CEE5970_Midterm-Soln2010 - CEE 5970 Risk Analysis and...

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CEE 5970 Risk Analysis and Management Evening Midterm Exam March 11, 2010 r Test is open book and open notes. You have 90 minutes to complete this 90 point exam. Please show readable work. 1. (7 pts) The sinking of the Titanic has received tremendous attention. Describe 3 aspects of the loss of the Titanic that made it such an unprecedented and significant catastrophe in 1912. What were the 3 most critical factors that resulted in so few passengers making it into lifeboats (and thus to safety)? <Remember Prof. Stedinger’s remarks about essays.> 2. (9 pts) Recently food poisoning was identified as an important health threat in the United States affecting one in four American’s every year causing 5,000 deaths (AP 19 Feb. 2010). Propose 3 quantitative criteria that would be useful for comparing different aspects of the risk of food poisoning, automobile accidents and smoking in modern urban life. Specify what each of your 3 criterion emphasizes. 3. (4 pts) Over the last 100 years, the population of the United States has increased from 76 million in 1900, to 280 million in 2000. But if one looks at the number of cancer deaths, we have gone from 50,000 deaths per year, to 600,000 in 2000. This is an alarming increase. Explain how we should understand this explosion in the number of US cancer deaths. 4. (12 pts) Prof. Stedinger is distressed by the number of e-mails he receives that attempt to get him to reveal confidential information (passwords, birth date, SS#). He averages 3 serious attempts to get him to divulge critical personal information every week (one week = 7 days). Imagine that such attempts can be described as a Poisson process over the 168 hours in a 7-day week. a) What is the mean and variance of the number of days that will pass until 25 of these attempts occur? b) What is the probability of having exactly 3 such attempts in the next 72 hours? What is the mean and variance of the number of attempts in a 72 hour period? c) Why might a Poisson process be a reasonable model for the arrival of these attempts? 5. (8 pts) Consider the fault tree below. F G System Failure A B a) If all components have a 1% failure probability, what is the system’s reliability. b) If you could decrease the failure probability of two components to 0.3%, which two should you pick to most improve system reliability? c) DRAW a network diagram that represents the operation of this system.

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CEE 5970 Risk Analysis and Management – Midterm 2010 Page 2 of 3 6. (12 pts) Consider the reliability of the system described by the network below: G C D B F A E H K a) What are ALL the minimal cut sets with 3 or fewer components? b) If K has a failure probability of 0.5%, and all other components fail with a probability of 5.0%, what approximately is the reliability of entire system? c) If you can decrease the failure probability of 1 component [not K] from 5% to 1%,
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CEE5970_Midterm-Soln2010 - CEE 5970 Risk Analysis and...

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