k • western Electric Company INCORPORATED -~ - This Handbook, as indicated in the "Foreword," was prepared to assist Western Electric people in performing Western Electric Company work. Others elsewhere may also think it useful as a guide for applying statistical quality control. The Company has printed a limited number of copies beyond its own requirements to meet such interest. These copies are available at $7.50, postage paid. Inquiries may be addressed to Superintendent, Quality Assurance, Western Electric Company, Inc., 222 Broadway, New York N. Y. 10038. The Handbook is not for sale through ordinary commercial channels. Western Electric Company, Inc. © BY WESTERN 1956 ELECTRIC Co., INC. First Edition 1956 Second Edition 1958 PRINTED IN THE UNITED STATES OF AMERICA BY THE MACK PRINTING COMPANY, EASTON, PENNSYLVANIA