PREFACE a 
tific vocational guidance cannot function without a knowl- 
edge of the abilities required for the different occupations 
and of the methods for measuring these abilities. 
Studies carried on with the technique here outlined will 
therefore be of value not only to employer and applicants, 
but also to those who give vocational and educational coun- 
sel, since these researches add to available knowledge of 
means for measuring vocational aptitude and of the require- 
ments for success in the occupations studied. 
We are happy to acknowledge our obligations to numerous 
investigators in industry and in the universities, both here 
and abroad. Many are mentioned in the text or in the 
bibliography. In particular we think of the pioneers in per- 
sonnel research who were at the Carnegie Institute of Tech- 
nology for shorter or longer periods between 1915 and 1923, 
during the presidency of Dr. A. A. Hamerschlag: Professors 
Scott, Miner, Thurstone, Whipple, Gordon, Charters, 
Yoakum, Strong, Stevenson, Lovelace, Schoen, Kenagy, 
Craig, and their associates and students, including, among 
many others, Doctors Beatty, Ruml, Hansen, Robinson, 
Bills, Moore, Ream, and Manson. They have shared in the 
evolution of this manual. For reading the manuscript and 
offering sound suggestions, we are grateful to Professors 
E. L. Thorndike and A. W. Kornhauser. 
For permission to reproduce tables or charts, we are 
indebted to Doctors Thurstone, Kelley, Scott, and Moede, 
the Adjutant General of the United States Army, the Life 
Insurance Sales Research Bureau, the Dennison Manufac- 
turing Company, the General Electric Company, the Mac- 
millan Company, the World Book Company, the Popular 
Science Monthly, and the Journal of Applied Psychology. 
WarLTter VAN DYKE BINGHAM 
Max FrevD 
New York, July 26, 1926 
Vil