(1 point) A statistics professor wants to compare today\'s students with those 2

Question

(1 point) A statistics professor wants to compare today's students with those 25 years ago. All of his current students' marks are stored on a computer so thathe can easily determine the population mean. However, the marks 25 years ago reside only in his musty files. He does not want to retrieve all the marks and will be satisfied with a 93% confidence interval estimate of the mean mark 25 years ago. If he assumes that the population standard deviation is 11, how large a sample should he take to estimate the mean to within 4 marks? Sample Size =

Explanation / Answer

93% CI of is x+-z*/sqrt(n)

Mean within 4 is 2z*/sqrt(n) =4

sqrt(n) = 2z*/4

We have = 11 and z= 1.812 at 93% CI

So, sqrt(n) = 2*1.812*11= 39.864

n = 1590

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