# hw2_answer_econ120a_su07 - Economics 120A Professor Yongil...

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Economics 120A Name: ________answer________________ Professor Yongil Jeon Summer 2007 Student ID#: _________________________ Answer to Homework #2 – Summer 2007 (Final Exam, Summer 2006) Answer all questions on separate paper. This problem set should be handed in to TA Deniz Kebabci at the beginning of your review session on Tuesday, July 31, 2007. Problem sets may not be handed in once solutions have been distributed. Please write down your name and PID clearly. Good luck! 1-a) (3 points) The standard normal probability table A) is equivalent to a t distribution if the sample size is less than 30. B) shows a normal distribution with standard deviation equal to zero. C) is used to make inference for all normally distributed random variables. D) None of the above. Answer: C 1-b) (3 points) The sampling distribution of the sample mean, when sampling from a normal population with mean µ and variance σ 2 is: A) normally distributed with mean µ and variance σ 2 . B) normally distributed with mean µ and variance s 2 . C) normally distributed with mean µ and variance σ 2 /n. D) normally distributed with mean 0 and variance 1. Answer: C 1-c) (3 points) Suppose that you mistakenly move the decimal point to the right one digit in data from a normal population with a mean of zero. What happens to the standard deviation? A) Data with mistake has standard error ten times the original. B) Data with mistake has same standard error as the original. C) Data with the mistake has twice the standard error of the original. D) Data with the mistake has one hundred times the standard error of the original. Answer: A

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2 Answer to HW #2, ECON 120A, Summer 2007 1-d) (3 points) Which probability distribution is appropriate for testing hypotheses concerning an unknown population mean when the sample variance is used to estimate the population variance? A) The normal distribution with mean µ and variance σ 2 . B) The normal distribution with mean 0 and variance 1. C) The standard normal distribution. D) The t distribution with n-1 degrees of freedom. Answer: D 1-e) (3 points) Which of the following is not true regarding the Central Limit Theorem?
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hw2_answer_econ120a_su07 - Economics 120A Professor Yongil...

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