35. The quadratic mean (or root mean square, or R.M.S.) is usually used in physical applications. In power distribution systems, for example, voltages and currents are usually referred to in terms of their R.M.S. values. The quadratic mean of a set of values is obtained by squaring each value, adding the results, dividing by the number of values n, and then taking the square root of that result, as indicated below:

Find the R.M.S. of these power supplies (in volts) obtained from the author’s home generator: 111.2, 108.7, 109.3, 104.8, 112.6.

Quadratic mean 5

Å

Sx2 n

>

>

n S

1 x

51 51, 51 3-2 Measures of Center 91 92 Chapter 3 Statistics for Describing, Exploring, and Comparing Data