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Unformatted text preview: Solutions to 120B Midterm B00 Section Multiple Choice 1. c 7. b 2. d 8. b 3. b 9. d 4. a 10. b 5. b 11. a 6. c 12. b Problems: (1) a. 99% confidence interval for the average earnings in the entire population is 434.49 2.58 1744 67 . 294 = 434.49 18.20 = (416.29, 452.69). Based on the sample at hand, the best guess for the population mean is $434.49. However, because of random sampling error, this guess is likely to be wrong. Instead, the interval estimate for the average earnings lies between $416.29 and $452.69. With 99% confidence, we can conclude that the true population average earning is between $416.29 and $452.69. I.e., if I draw a large number of samples and use them to build 99% confidence intervals, the true population mean would be contained in 99% of those intervals. b. For a 90% confidence interval, the only change in the calculation of the confidence interval is to replace 2.58 by 1.64. Hence the confidence interval is smaller. A smaller interval implies, given the same average earnings and the standard deviation, that the statement will be false more often. The larger the confidence interval, the more likely it is to contain the population value....
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This note was uploaded on 08/14/2008 for the course ECON 120B taught by Professor Jeon during the Spring '08 term at UCSD.
- Spring '08