The paper outlines some of the elementary statistical methods, and illustrates their application to a variety of problems encountered in the field of electricity supply.Particular attention is given to methods of describing group performance, such as by classification, and graphic representation of the frequencies at which the classified values of a variable characteristic occur, and by kindred graphs; and to the method of estimating the performance of an indefinitely large group by investigating a limited sample only. Various methods of sample selection are indicated and a number of elementary formulae added, which may enable the supply engineer to choose economic sample-sizes and to assess the significance of results. A collection of frequency diagrams illustrate conditions met with in practice. Reference is also made to the elements of correlation and regression analysis.