Control Charts and Process Capability

July 17, 1994

INTRODUCTION

The purpose of this paper is to provide a guide for applying quality control principles to our work of serving customers, communities, and shareholders as we continually improve our work, in our jobs and in our organization. It is intended to describe the processes which will cause us to preserve the essential features of the quality our customers rely on as they have become accustomed. Whether working in customer service at the front line, or in staff, managers must control our various work processes, in an economic system of cause and effect. In the history of the AT&T Bell System, the methods that made it possible for that organization to expand in providing service across the world, and to make the parts that made the services work, it attained the reputation of “best in the world” came from the evidence of science and service.

Ten years ago, that Bell System was broken into multiple pieces, yet that does not mean that what we learned from that history of service and science is abandoned. To a certain degree, we can look at these methods that contributed the most to making that history successful. Much of the following material is based on learning delivered over the last decades to supervisors, engineers, staff, executives, and key people in management of the Bell operating companies..

We are witness to the transformation of our industry, informed by the past and connected to it through scientific management, and the responsibilities that come with it as we have moved from the Industrial Age to the Information Age, and perhaps even to the age of “Knowledge”.

The actual science of management and related mathematics described in this paper have been used in all types of industry since they were developed decades ago at Bell Laboratories by Dr. Walter Shewhart.. What follows is on the method of the control chart, a model of economic operations for managing processes economically in any effort to determine whether the needed qualities of whatever is measured as important to a service, process or product can be sustained. Time and money spent for training and improvement will be wisely invested at the exact process where they make the greatest impact on the Ameritech and AOCs (Ameritech Operating Cos.)