The head librarian at the National Library of Australia 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 for a 95% confidence interval,approximately how large a sample did her assistant use to determine the interval estimate?
A) 11
B) 13
C) 4
D) 125

Question

Quizplus · Accepted Answer

The sample size can be calculated using the formula: n = (Z^2 * s^2) / (E^2)where Z is the z-score for the desired confidence level, s is the population standard deviation, and E is the margin of error.In this case, the confidence level is 95%, so the z-score is 1.96. The population standard deviation is 150 books checked out per day, and the margin of error is (920 - 740) / 2 = 90 books checked out per day.Plugging these values into the formula, we get: n = (1.96^2 * 150^2) / (90^2) = 11.96Since we cannot have a fraction of a sample, we round up to the nearest whole number, which is 12.

The Head Librarian at the National Library of Australia Has