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Unformatted text preview: Economic Statistics Exam 3b Last name: Spring 2009 First name: PPID: Section number: Please sign that you abide by the honor pledge: This exam contains twenty short answer questions ( worth 6 points each ) and four long answer questions ( worth 15 points each ) . Show your work clearly to be eligible for partial credit. In all problems where you need to make a calculation, simplify your answer as much as convenient. In questions with multiple parts, you should respond as if your answers to previous parts were correct. Some PDFs: Some probabilities: f ( x ) = 1 2 !" 2 e # ( X # ) 2 " 2 P [ x ! a ] = e " # a f ( x ) = 1 u ! ! P [ X ] = x e ! X ! f ( x ) = ! E " ! x P [ ] = N ! !( N ! )! p (1 ! p ) N ! Short Questions ( 6 points apiece ) 1. What two things we interpret from the correlation coefficient? 2. X comes from a normal distribution with a mean of 10 and variance of 4 . If you collect a random sample of 6 people, what is the probability that your sample mean is less than 9 ? Econ 400 Exam 3, page 2 of 10. 3. What is wrong with creating a pie chart, and then labeling the percentage of the sample that belongs in each wedge? 4. A random variable X takes on the values 1,2,3,4,5 with equal probability. What is the variance in X ? 5. The salary of university graduates is distributed with a mean of $ 45,000 and a standard deviation of $ 20,000. Using Chebyshevs Theorem, state what fraction of graduates earns between $ 15,000 and $ 75,000. 6. Give me the five number summary of these numbers: 1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,1597 7. Using a high confidence level when testing a hypothesis means a low chance of what , but a high chance of what else? Econ 400 Exam 3, page 3 of 10. 8. Only 10% of suspected swine flu cases turn out to be the swine flu. Public health officials invent a new rapid test for the disease. For people who do in fact have swine flu, the test gives a positive result 99% of the time. For people without the disease, the test has a 25% rate of ( false ) positive results. Given that a person tests positive, what is the chance that he has swine flu?...
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