First published in 1940, this book was designed to explain as simply as possible how to perform the calculations involved in common statistical methods. Although not meant as a treatise on the theory of statistics, it nevertheless offered sufficient theory to enable the student to understand the use and application of the methods described. Whilst the book was chiefly addressed to students of the biological sciences, especially psychology, the methods described are fundamental to statistical work and could also prove useful to anyone needing to make use of elementary statistical methods. More than ten years after its original publication, a second edition was produced in 1952. This edition corrected a number of small arithmetical errors and took into account new statistical methods that had been developed. It is this second edition which is reproduced here.