ERNEST HORN, Ph.D.PREFACEERNEST J. ASHBAUGH, Ph.D.
ASSOCIATE PROFESSOR OF EDUCATION AND CHIEF OF THE
BUREAU OF EDUCATIONAL TESTS AND MEASUREMENTS
THE STATE UNIVERSITY OF IOWA
PHILADELPHIA, LONDON, CHICAGO
J. B. LIPPINCOTT COMPANY
COPYRIGHT, 1920, BY J. B. LIPPINCOTT COMPANY
PRINTED BY J. B. LIPPINCOTT COMPANY
AT THE WASHINGTON SQUARE PRESS
PHILADELPHIA, U. S. A.