8. As the sample size increases, the margin of error increases a. b. decreases c. stays the same d. increases or decreases depending on the size of the mean 9. A sample of 225 elements from a population with a standard deviation of 75 is selected. The sample mean is 180. The 95% confidence interval for u is a. 105.0 to 225.0 b. 175.0 to 185.0 c. 100.0 to 200.0 d. 170.2 to 189.8 10. It is known that the variance of a population equals 1,936. A random sample of 121 has been taken from the population. There is a .95 probability that the sample mean will provide a margin of error of a. 7.84 b. 31.36 c. 344.96 d. 1,936 11. A random sample of 144 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is a. 15.2 to 24.8 b. 19.200 to 20.800 c. 19.216 to 20.784 d. 21.2 to 22.8 12. The sample size needed to provide a margin of error of 2 or less with a .95 probability when the population standard deviation equals 11 is a. 10 b. 11 c. 116 d. 117 13. It is known that the population variance equals 484. With a 0.95 probability, the sample size that needs to be taken if the desired margin of error is 5 or less is a. 25 b. 74 c. 189 d. 75 14. The following random sample from a population whose values were normally distributed was collected. 10 12 18 16 The 80% confidence interval for u is a. 12.054 to 15.946 b. 10.108 to 17.892 c. 10.321 to 17.679 d. 11.009 to 16.991 15. In a random sample of 144 observations, P=0.6. The 95% confidence interval for P is a. 0.52 to 0.68 b. 0.144 to 0.200 c. 0.60 to 0.70 d. 0.50 to 0.70