## Elementary Statistics (12th Edition)

Range is the difference of the maximum and minimum of the set: range=49-12=37 minutes. Calculated by calculator, the mean is: 20.98 minutes. The variance is the sum of the differences of each value and the mean on the power of two, divided by the number of values minus 1: variance=$\frac{(30-20.98)^2+(19-20.98)^2+...+(30-20.98)^2}{50-1}=85.5$ minutes. The standard deviation is the square root of the variance: standard deviation=$\sqrt{85.5}=9.247$ minutes.