Math 221: Statistics Exam Questions with Correct Answers

From a random sample of 58 businesses, it is found that the mean time the owner spends on administrative issues each week is 21.69 with a population standard deviation of 3.23. What is the 95% confidence interval for the amount of time spent on administrative issues? A. (19.24, 24.14) B. (21.78, 22.60) C. (20.86, 22.52) D. (20.71, 22.67) Correct Answer C. (20.86, 22.52) If a confidence interval is given from 45.82 up to 55.90 and the mean is known to be 50.86, what is the margin of error? 2.52 5.04 45.82 10.08 Correct Answer 5.04 If a computer manufacturer needed a supplier that could produce parts that were very precise, what characteristics would be better? narrow confidence interval at low confidence level narrow confidence interval at high confidence level wide confidence interval with high confidence level wide confidence interval with low confidence level Correct Answer narrow confidence interval at high confidence level Which of the following are most likely to lead to a wide confidence interval? small standard deviation small sample size large mean large sample size Correct Answer small sample size If you were designing a study that would benefit from data points with high values, you would want the input variable to have: a large sample size a large mean a large standard deviation a large margin of error Correct Answer a large mean The 95% confidence interval for these parts is 56.98 to 57.05 under normal operations. A systematic sample is taken from the manufacturing line to determine if the production process is still within acceptable levels. The mean of the sample is 56.99. What should be done about the production line? Keep the line operating as it is inside the confidence interval Stop the line as it is inside the confidence interval Stop the line as it is outside the confidence interval