Ramdomly selected students participated in an experiment to

Ramdomly selected students participated in an experiment to test their ability to determine when on minute (or sixty seconds) has passed. Forty students yielded a sample mean of 60.2 seconds. Assuming that Estandar deviation= 8.8 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 u?

_____< u < ____ ( type integers or decimals rounded to one decimal place as neede)

Solution

Given a=1-0.95=0.05, Z(0.025) = 1.96 (from standard normal table)

So the lower bound is

xbar - Z*s/vn=60.2 -1.96*8.8/sqrt(40) =57.47285

So the upper bound is

xbar + Z*s/vn=60.2 +1.96*8.8/sqrt(40) =62.92715