An economist is interested in studying the incomes of consumers in a particular country. The population standard deviation is known to be 1,000. A random sample of 50 individuals resulted in a mean income of 15,000. What total sample size would the economist need to use for a 95 confidence interval if the width of the interval should not be more than 100?
A) n = 40 B) n = 1537 C) n = 385 D) n = 20
Question 2
The head librarian at the Library of Congress has asked her assistant for an interval estimate of the mean number of books checked out each day. The assistant provides the following interval estimate: from 740 to 920 books per day. If the head librarian knows that the population standard deviation is 150 books checked out per day, and she asked her assistant to use 25 days of data to construct the interval estimate, what confidence level can she attach to the interval estimate?
A) 99.7 B) 99.0 C) 95.4 D) 98.0
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