The Road to Quality Control

The Industrial Application of Statistical Quality Control by Homer M. Sarasohn

Nicholas Fisher, Yutaka Tanaka, William Woodall

• Publisher: Wiley
• Year: 2018
• Print ISBN: 9781119514930
• eBook ISBN: 9781119514985
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Quality Control in Engineering
• Index: Technology & Engineering

Professor Woodall's essay shows that this book represents a remarkable contribution, even by today's standards, because of its contemporary thinking about the relationship between the specific topic of SQC and the broader company context of Quality Management. It also demonstrates the remarkable awareness of at least some young US engineers in the post-war period about the vital role of Statistical Quality Control in establishing and maintaining a competitive position. The book reveals that there was unsuspected knowledge extant immediately post-war, about the importance of Statistical Quality Control when appropriately applied in an industrial setting. It also helps to correct wide-spread historical misconceptions about who specifically was responsible for helping Japanese industry get back on its feet post-war, a task assigned to General Douglas Macarthur by President Truman and how Macarthur was indebted to Sarasohn.

II
Probability and Statistical Inference

In order to understand Statistical Quality Control properly, you need to know about statistical inference and Probability. In the theory of Probability, the probability of an event occurring is based on the hypothesis that states “the results occurring under the same conditions are considered the same”. This is a fundamental law of Science: the belief that you'll always get the same results if you repeat the experiment under precisely the same conditions. However, in the case of products made in factories, it cannot be the same as what you do in the laboratory, where it is easy to set the same conditions. Although we try to control the operating conditions in several ways, such as managing the manufacturing process, doing process analysis, coaching people in standard operating procedures, or by trying other control methods, the products produced frequently don't meet the required standard because of a variety of problems caused by the bad effects of those trials themselves. Even if the manufacturing conditions at one time are consistent with those at another time, they are only “relatively the same”. Therefore, it is difficult to avoid variation in the quality as it's impossible to equalize the characteristics of each one and, moreover, it is hard to do this in an economical way. However, we not only can, but we must, minimize, although not exactly, the amount of variability in the quality of products in a unit or lot, as we explain precisely in Chapter III. This is the purpose of quality control.

Let's explain this idea with an example. Suppose you strike a match. It ignites and produces some smoke. And you expect to get the same result if you strike another one; that is, it will also ignite and produce smoke. Now, you take out a match and when the second match actually flames up, you'll think that the conditions for the two separate actions were the same because they produced the same results, and you'll also think that all matches in the box will be of the same quality.

However, if the second match hasn't ignited, you would suspect that the operating condition was not the same as for the first match. Then again, what type of conclusion can you reach if the second one hasn't ignited but the ...

Table of contents

• Cover
• Table of Contents
• Contents – Summary
• Translators' Preface
• Foreword
• I Introduction
• II Probability and Statistical Inference
• III Sampling Inspection
• IV Application of Sampling Inspection
• V Quality Control of the Production Process
• AppendixStatistical Tables for Sampling Inspection
• Thoughts on The Road to Quality Control – The Industrial Application of Statistical Quality Control by Homer M. Sarasohn
• Homer Sarasohn and American Involvement in the Evolution of Quality Management in Japan, 1945–1950*
• End User License Agreement