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Unformatted text preview: Sample Exam II STAT 211 (Fall 2010) Name : Student ID : • You have 75 minutes to complete this test. • You may use the provided sheets, all appropriate tables (if any) and a calculator. • If I provide partial results—assume they are correct and use them even if they are not. • If there is no correct answer or if multiple answers are correct, select the best answer. • This test consists of 20 questions. Make sure you have all questions and Good luck! 1 1. Household electricity bill is $100 per month on average, with variance 400. We sample 100 families, what is the probability that the average we calculate from these 100 families is larger than $105? A. 0.4880 B. 0.1056 C. 0.8944 D. 0.9938 E. 0.0062 2. Assume X and Y are two independent standard normal random variables. What is the mean of X + Y ? A. 2. B. 0. C. √ 2. D. insufficient information to calculate. E. none of the above. 3. Assume X and Y are two independent standard normal random variables. What is the standard deviation of X + Y ? A. 2. B. 0. C. √ 2 . D. insufficient information to calculate. E. none of the above. 4. Suppose the joint pdf of X and Y is p ( x, y ) = 1 π e x 2 +4 xy 5 y 2 . What is the marginal pdf of Y ? A. √ 3 2 √ π e 3 4 x 2 . B. 1 √ π e y 2 . C. 1 √ 2 π e x 2 . D. 1 √ π e y 2 . E. None of the above is correct. 5. Continue from the previous problem. What is the marginal pdf of X ?...
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 Spring '07
 Parzen
 Normal Distribution, Variance, Shanghai, E.

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