ABSTRACT
Two scientific sources have been drawn on heavily in the efforts to improve psychological and educational measurements. One of these sources is general psychology; the other is the science of statistics. General psychology has been engaged since the middle of the nineteenth century in developing methods of measuring mental processes. For the past fifty years mathematicians in co-operation with students of a number of special sciences, especially the biological and social sciences, have made important contributions to the technical science of statistics. From both of these sources so much light has been thrown on the processes of learning and on mental development that educational psychology has found it highly advantageous to adopt the methods of psychological and statistical measurement for the solution of its problems.
