exam1_answer_econ120a_su07

exam1_answer_econ120a_su07 - Economics 120A July 23, 2007...

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Economics 120A Name: _________________________ July 23, 2007 Student ID#: _____________________ Answer to Midterm Exam: Econometrics (Econ 120A) 1. True/False (2 points each) 1. The optimal solution to a mathematical model is always the policy that should be implemented by the company. Answer: False 2. Microcomputers have made most quantitative approaches to decision making more accessible to even moderate size firms. Answer: True 3. Past data might be used to test the validity of a mathematical model. Answer: True 4. Pr(A|B)=1 – Pr(B|A) for all events A and B. Answer: False 5. If A and B are mutually exclusive, Pr(A) + Pr(B) must equal 1. Answer: False 6. The probability of at least one head in two flips of a coin is 0.75. Answer: True 7. If a random variable can take on a countably infinite number of values, one would use a discrete distribution. Answer: True 8. The variance of a random variable will always be greater than its standard deviation. Answer: False 9. The binomial distribution is most symmetric when p equals 0.5. Answer: True
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2 Answer to MIDTERM EXAM, ECON 120A, SUMMER 2007 10. A Bernoulli process is a sequence of independent trials with two possible outcomes whose probabilities can change between trials. Answer: False 2. (10 points) . Prove that the average of deviations about the sample mean is zero. Answer: The question asks you to show that for sample size n, that the average of deviations about the sample mean is zero: Using the definition of the sample mean, this can easily be shown: () 1 1 0. n i i n X X = = 11 1 1 0. nn n ii i n XX X X == =  =− =   ∑∑
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3 Answer to MIDTERM EXAM, ECON 120A, SUMMER 2007 3. (10 points)
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exam1_answer_econ120a_su07 - Economics 120A July 23, 2007...

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