Excerpt from The Psychological Monographs, And, Association Tests: Being a Part of the Report of the Committee of the American Psychological Association on the Standardizing of Procedure in Experimental Tests The tests which we have thus selected are in some degree ana logons to tested reagents in chemistry. They make no claim, indeed, to be chemically pure; that is to say, they can not be guaranteed to give a true measure of every individual tested. Any mental test is sure to' be vitiated in some cases either by peculiarities of an individual's training and information, or by the accidental variations to which mental performance is subject from moment to moment. These sources of error exist in all measurements of intellectual abilities. In the face of such diffi culties, some investigators have felt it necessary to retreat from a quantitative attack on individual psychology; while others, more hopeful, have sought to neutralize the error of the single measurement by statistical methods. In the study of class differ ences, they have relied on averages from large groups; and in the study of correlations, they have endeavored to correct for the attenuation resulting from chance errors in the single measure ments. But either reliance on the averages of large groups or reliance on Spearman's attenuation formulae is a reliance on probability, and therefore sure to be justified in the long run, but equally sure to be treacherous somewhere or other. Certainly, therefore, it is wise to eliminate from the tests all possible sources of error; though other sources of error still remain, yet for every defect eliminated there is an increase in the reliability of the in dividual measure, and so of the final result. Now most of the tests hitherto employed involve sources of error which can be eliminated once they are detected in practise. Many of these Sources of error are little details in the construction of the tests; for example, one or two of the words selected as stimuli may have been ambiguous, or unfamiliar to many subjects. Our work has very largely consisted in attention to such details; and while we cannot hope to have attained perfection of detail, we are sure that we have taken some steps in that direction. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.