Math 221 Statistics Exam Questions With Complete Solution

Math 221 Statistics Exam Questions With Complete Solution 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 ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS 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 ANSWERS 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 Keep the line operating as it is outside the confidence interval - CORRECT ANSWERS Keep the line operating as it is inside the confidence interval In a sample of 57 temperature readings taken from the freezer of a restaurant, the mean is 29.6 degrees and the population standard deviation is 2.7 degrees. What would be the 80% confidence interval for the temperatures in the freezer? (31.90, 32.44) (29.14, 30.06) (24.25, 35.05) (26.91, 32.31) - CORRECT ANSWERS (29.14, 30.06) What is the 99% confidence interval for a sample of 36 seat belts that have a mean length of 85.6 inches long and a population standard deviation of 2.5 inches? (80.6, 90.6) (83.1, 88.1) (84.4, 86.8) (84.5, 86.7) - CORRECT ANSWERS (84.5, 86.7) If two samples A and B had the same mean and standard deviation, but sample A had a larger sample size, which sample would have the wider 95% confidence interval? Sample B as its sample is more dispersed Sample B as it has the smaller sample Sample A as it comes first Sample A as it has the larger sample - CORRECT ANSWERS Sample B as it has the smaller sample Why might a company use a lower confidence interval, such as 80%, rather than a high confidence interval, such as 99%? They are in the medical field, so cannot be so precise They make computer parts where they are too small for higher accuracy They track the migration of fish where accuracy is not as important They make children's toys where imprecision is expected - CORRECT ANSWERS They track the migration of fish where accuracy is not as important Determine the minimum sample size required when you want to be 95% confident that the sample mean is within two units of the population mean. Assume a population standard deviation of 4.3 in a normally distributed population. 20 22 16 18 - CORRECT ANSWERS 18