## Essentials of Statistics (5th Edition)

$8.104$
$\alpha=1-0.98=0.02.$ $\sigma$ is not known, hence we use the t-distribution with $df=sample \ size-1=50-1=49\approx50$ in the table. $t_{\alpha/2}=t_{0.01}=2.403.$ Margin of error:$t_{\alpha/2}\cdot\frac{s}{\sqrt {n}}=2.403\cdot\frac{5.013}{\sqrt{50}}=1.704.$ Hence the confidence interval:\$9.808-1.704=8.104