## Elementary Statistics (12th Edition)

Range is the difference of the maximum and minimum of the set: range=2.95-0=2.95 Richter scale. Calculated by calculator, the mean is: 1.184 Richter scale. 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=$\frac{(0.7-1.184)^2+(2.2-1.184)^2+...+(1.39-1.184)^2}{50-1}=0.34 Richter scale.$ The standard deviation is the square root of the variance: standard deviation=$\sqrt{0.34}=0.583 Richter scale$. By The Range Rule of Thumb the standard deviation is one fourth of the range: $\frac{2.95}{4}=0.7375$. This estimated standard deviation is a bit more than the real standard deviation.