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Unformatted text preview: Economic Statistics Exam 2 Last name: November 2, 2006 First name: PPID: Circle class time: 9:30- 11:00 12:30- 2:00 Please sign that you abide by the honor pledge: This exam contains fifteen short answer questions ( worth 4 points each ) and four long answer questions ( worth 15 points each ) . Please answer in the space provided; if you need more room, indicate clearly that the answer is continued on the back of the page. In all problems where you need to make a calculation, simplify your answer as much as possible. Show your work clearly to be eligible for partial credit. Some PDFs: Some probabilities: f ( x ) = 1 2 !" 2 e # ( X # μ ) 2 " 2 P [ x ! a ] = e " # a f ( x ) = 1 u ! ! P [ X ] = μ x e ! μ X ! f ( x ) = ! e " ! x P [ X ] = N ! X !( N ! X )! p X (1 ! p ) N ! X Short Questions ( 4 points apiece ) 1. X is a random variable with a continuous distribution. Its probability density function is some function, f ( x ) . How would we find the probability that X is between two values ( for example, between 2.13 and 4.56 ) , using the PDF? 2. The sum of many small random variables tends to have a normal distribution, regardless of the distribution of the individual random variables. What is the analogous statement for the log- normal distribution? Econ 400 Midterm 2, page 2 of 8. 3. What is the difference between an estimate and an estimator? 4. After a long night of trick- or- treating, the number of candies in my bag is a random variable, distributed normally with mean of 300 and variance of 400. What is the chance that I have fewer than 250 candies in my bag?...
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- Spring '08
- Normal Distribution, Probability theory, c. Al