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Unformatted text preview: Chapter 10: Introduction to Inference 1. A 95% confidence interval for the mean of a population is computed from a random sample and found to be 9 3. We may conclude A) that there is a 95% probability that is between 6 and 12. B) that 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) that 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 the above. Ans: C Section: 10.1 Estimating with Confidence 2. The records of all 100 postal employees at a postal station in a large city showed that the average amount of time these employees had worked for the U.S. Postal Service was J = 8 years. Assume that we know that the standard deviation of the amount of time U.S. Postal Service employees have spent with the Postal Service is approximately normal with standard deviation = 5 years. A 95% confidence interval for the mean time the population of U.S. Postal Service employees has spent with the postal service based on these data is A) 8 0.82. B) 8 0.98. C) 8 9.80. D) not trustworthy. Ans: D Section: 10.1 Estimating with Confidence Page 125 Chapter 10: Introduction to Inference 3. The scores of a certain population on the Wechsler Intelligence Scale for Children (WISC) are thought to be normally distributed with mean and standard deviation = 10. A simple random sample of 10 children from this population is taken, and each is given the WISC. The 95% confidence interval 10 1.96 10 x for is computed from these scores. A histogram of the 10 WISC scores is given below. Based on this histogram, we would conclude that A) the 95% confidence interval computed from these data is very reliable. B) the 95% confidence interval computed from these data is not very reliable. C) the 95% confidence interval computed from these data is actually a 99% confidence interval. D) the 95% confidence interval computed from these data is actually a 90% confidence interval. Ans: B Section: 10.1 Estimating with Confidence 4. A 90% confidence interval for the mean of a population is computed from a random sample and is found to be 9 3. Which of the following could be the 95% confidence interval based on the same data? A) 9 2. B) 9 3. C) 9 4. D) Without knowing the sample size, any of the above answers could be the 95% confidence interval. Ans: C Section: 10.1 Estimating with Confidence Page 126 Chapter 10: Introduction to Inference 5. An agricultural researcher plants 25 plots with a new variety of corn. The average yield for these plots is J = 150 bushels per acre. Assume that the yield per acre for the new variety of corn follows a normal distribution with unknown mean and standard deviation = 10 bushels per acre. A 90% confidence interval for is A) 150 2.00. B) 150 3.29. C) 150 3.92. D) 150 32.90....
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This note was uploaded on 03/30/2008 for the course STAT 155 taught by Professor Unknown during the Spring '07 term at UNC.
 Spring '07
 unknown
 Probability

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