itn Ars - hak PREFACE TO THE FIRST EDITION. Tae following chapters are based on the courses of instruction given during my tenure of the Newmarch Lectureship in Statistics at University College, London, in the sessions 1902-1909. The variety of illustrations and examples has, however, been increased to render the book more suitable for the use of biologists and others besides those interested in economic and vital statistics, and some of the more difficult parts of the subject have been treated in greater detail than was possible in a sessional course of some thirty lectures. For the rest, the chapters follow closely the arrangement of the course, the three parts into which the volume is divided corresponding approximately to the work of the three terms. To enable the student to proceed further with the subject, fairly detailed lists of references to the original memoirs have been given at the end of each chapter: exercises have also been added for the benefit, more especially, of the student who is working without the assistance of a teacher. The volume represents an attempt to work out a systematic introductory course on statistical methods—the methods available for discussing, as distinct from collecting, statistical data—suited to those who possess only a limited knowledge of mathematics : an acquaintance with algebra up to the binomial theorem, together with such elements of co-ordinate geometry as are now generally included therewith, is all that is assumed. I hope that it may prove of some service to the students of the diverse sciences in which statistical methods are now employed. My most grateful thanks are due to Mr R. H. Hooker not only v1l