$\"\"$

The confidence interval is $\"\"$ .

Sample standard deviation is $\"\"$ .

$\"\"$ value is $\"\"$ .

Work backward to determine the degree of freedom.

The error estimate $\"\"$ is equal to the one half of the range of the confidence interval $\"\"$

$\"\"$

Find the value of $\"\"$ :

$\"\"$ .

$\"\"$

The degrees of freedom are $\"\"$ .

$\"\"$

The degrees of freedom are $\"\"$ .