$\"\"$

\

The number of students are $\"\"$ .

\

The average messages send or receive is $\"\"$ text messages a day.

\

The standard deviation is $\"\"$ messages.

\

Find the maximum error of estimate for a $\"\"$ confidence level.

\

In a $\"\"$ confidence interval, $\"\"$ of the area lies in tail.

\

The corresponding $\"\"$ value is $\"\"$ .

\

Formula for maximumu error estimate is $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$ .

\

$\"\"$

\

Find the confidence interval.

\

The confidence interval CI for a population mean $\"\"$ is $\"\"$ .

\

Substitute $\"\"$ and $\"\"$ .

\

$\"\"$ .

\

$\"\"$ .

\

The confidence interval is $\"\"$ .

\

$\"\"$

\

The confidence interval is $\"\"$ .