PracticeFinal_soln

PracticeFinal_soln - Econ 2500 - Practice Final Solutions...

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Econ 2500 - Practice Final Solutions 1. (30 points) Multiple choice questions 1) A 95% confidence interval for the mean of a population is computed from a random sample and found to be 93 . We may conclude that A) There is a 95% probability that is between 6 and 12. B) There is a 95% probability that the true mean is 9 and there is a 95% chance that the true margin of error is 3. C) If we took many, many additional random samples and from each computed a 95% confidence interval for , approximately 95% of these intervals would contain . D) All of above. Answer C 2) Suppose that the population of the scores of all high school seniors that took the SAT-M (SAT math) test this year follows a normal distribution with mean and standard deviation 100 . You read a report that says, “On the basis of a simple random sample of 100 high school seniors that took the SAT-M test this year, a confidence interval for is 512 25.76 .” The confidence level for this interval is A) 90% B) 95% C) 99% D) Over 99.9% Answer C 3) Other things being equal, the margin of error of a confidence interval increases as A) The sample size increases. B) The confidence level decreases. C) The population standard deviation increases D) None of the above Answer C 4) The P-value of a test of a null hypothesis is A) The probability, assuming the null hypothesis is true, that the test statistic will take a value at least as extreme as that actually observed. B) The probability, assuming the null hypothesis is false, that the test statistic will take a value at least as extreme as that actually observed. C) The probability that the null hypothesis is true. D) The probability that the null hypothesis is false. Answer A
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Use the following information to answer questions 5-6: An SRS of 100 postal employees found that the average time these employees had worked for the postal service was 7 x years with standard deviation 2 s years. Assume the distribution of the time the employees have worked for the postal service is approximately normal with mean . Are these data evidence that has changed from the value of 7.5 years of 20 years ago? To determine this we test the hypotheses 0 : 7.5 vs. : 7.5 a HH  5) a 95% confidence interval for the mean time the population of postal service employees have spent with the postal service is A) 72 B) 7 1.984 C) 70 . 4 D) . 2 Answer C 6) Suppose the mean and standard deviation obtained were based on a sample of 25 postal workers rather than 100. The P -value would be A) Larger B) Smaller C) Unchanged because the difference between x and the hypothesized value 7.5 is unchanged.
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This note was uploaded on 08/29/2011 for the course ECON 2500 taught by Professor Xianghongli during the Winter '11 term at York University.

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PracticeFinal_soln - Econ 2500 - Practice Final Solutions...

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