Chapter 3.1, Problem 38EC

Quadratic Mean A useful mean in the physical sciences (such as voltage) is the quadratic mean (QM), which is found by taking the square root of the average of the squares of each value. The formula is

$\text{QM}=\sqrt{\frac{\Sigma X^2}{n}}$

The quadratic mean of 3, 5, 6, and 10 is

$\begin{array}{c}QM=\sqrt{\frac{3^2+5^2+6^2+{10}^2}{4}}\\ =\sqrt{42.5}\approx 6.519\end{array}$

Find the quadratic mean of 8, 6, 3, 5, and 4.