Randomly selected students participated in an experiment to

Randomly selected students participated in an experiment to test their ability to determine when one minute (or sixty seconds) has passed. Forty students yielded a sample mean of 59.1 seconds. Assuming that sigma = 10.9 seconds, Construct and interpret a 95% confidence interval estimate of the population mean of all students. What is the 95% confidence interval for the population mean mu?

Solution

Given a=0.05, Z(0.025) = 1.96 (from standard normal table)

So the lower bound is

xbar - Z*s/vn =59.1 - 1.96*10.9/sqrt(40) = 55.7

So the upper bound is

xbar + Z*s/vn =59.1 + 1.96*10.9/sqrt(40) =62.5

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