If a data set of n=115 has a mean of 9.74 and a population standard deviation of 2.93, what is the 95% confidence interval?

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Answer 1 · 2015-11-02T11:08:45

We are 95% confidence that the population mean lies between $10.27$ and $9.21$

95% Confidence interval is -

$mu=barx+-(SE . z)$

$SE =sigma/sqrtn=2.93/sqrt115=2.93/10.72=0.27$

$z$ value for 95% confidence

$z = 1.96$

Upper Limit:

$mu=9.74+(0.27 xx 1.96)$
$mu=9.74+0.53$
$mu=10.27$

Lower Limit:

$mu=9.74-(0.27 xx 1.96)$
$mu=9.74-0.53$
$mu=9.21$