Question

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1.       A sample of 210 one-year-old baby boys in the United States had a mean weight of 23.8 pounds. Assume the population standard deviation is 3.0 pounds. What is the upper bound of the 90% confidence interval for the mean lifetime of the components? Round to two decimals.

2.       Efficiency experts study the processes used to manufacture items in order to make them as efficient as possible. One of the steps used to manufacture a metal clamp involves the drilling of three holes. In a sample of 74 clamps, the mean time to complete this step was 48.9 seconds. Assume that the population standard deviation is 13 seconds. What is the lower bound of the 98% confidence interval? Round to one decimal place.

3.       In a simple random sample of 57 electronic components produced by a certain method, the mean lifetime was 1,188 hours. Assume that component lifetimes are normally distributed with population standard deviation 53 hours. What is the upper bound of the 95% confidence interval for the mean lifetime of the components? Round to the nearest integer.

4.       A college admissions officer takes a simple random sample of 106 entering freshmen and computes their mean mathematics SAT score to be 508. Assume the population standard deviation is 122. What is the lower bound of the 99% confidence interval? Round to the nearest integer.

Answer 1