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.. (4 points) You are constructing a confidence interval for a population mean. Which of the following case would NOT change confidence interval? (a) Standard deviation is increased from 13 to 25. (b) Sample size is decreased from 100 to 50. (c) Confidence level is increased from 90% to 95%. (d) Sample mean is increased from 25 to 30. - (4 points) You measure the lifetime of a random sample of 64 tires of a certain brand. In a follow-up study, more tires were available for testing, so you were able to measure the lifetimes of a random sample of 100 tires rather than 64. Which of the following statements is true? (a) The margin of error for your 99% confidence interval would increase (b) The margin of error for your 99% confidence interval would decrease. (c) The margin of error for your 99% confidence interval would stay the same, because the level of confidence has not changed. (d) The value of o would decrease. a (4 points) Suppose a researcher is interested in understanding the variation in price of store brand milk. A random sample of 36 grocery stores selected from a population and the mean price of store brand milk is calculated. The sample mean is $3.13 with a population standard deviation of $0.23. Construct a 95% confidence interval to estimate the population mean. (a) 3.03 to 3.23 (b) 3.12 to 3.14 (c) 3.05 to 3.21 (d) 2.90 to 3.36