Essentials of Statistics (5th Edition)

Variance:$99.141\ (\$)^2$. Standard deviation:$9.957 \$$Range:22.85\$$.
The mean can be counted by summing all the data and dividing it by the number of data: $\frac{55.99+69.99+48.95+48.92+71.77+59.68}{6}=59.22$: $\mu=59.22 \ \$.$Variance=$\frac{\sum (x-\mu)^2}{n}=\frac{(55.99-59.22)^2+(69.99-59.22)^2+...+(59.68-59.22)^2}{6}=99.141 \ (\$)^2.$ Standard deviation=$\sqrt{variance}=\sqrt{99.141 \ (\$)^2}=9.957 \$$Range=maximum value-minimum value=71.77 \-48.92 \=22.85\$$.