AS 3940-1990

Provides guidance on the selection and use of control charts for quality management, and is complementary to AS 3941, AS 3942 and AS 3943 which provide detailed operational procedures. Explains how control charts work, the application of average run length to control charting and the procedure for determining process capability. Outlines the probability models and sampling statistics underlying these charting methods.

This Standard provides guidance on the selection and application of quality control chart methods for process control and is complementary to AS 3941, AS 3942 and AS 3943 (which provide detailed operational procedures based on the use of either Shewhart control charts or cumulative sum (Cusum) techniques). It is designed for use by quality practitioners and other persons concerned with making decisions on charting technique.The Standard explains how control charts work, the types of risk involved, the reasoning behind the decision rules, and how the average run length gives a measure of their effectiveness. Other aspects covered are frequency of sampling, sample sizes, and methods for identifying types of variation. The Standard also provides an itemized procedure for the determination of process capability, which is an essential prerequisite to the achievement of process/quality control.The systematic approach given in this Standard has the principal objective of assisting development within industry of a sound appreciation of the relative merits of the many and various control methods currently available.As such, this Standard provides a basic reference for both industrial training and technical educational purposes irrespective of whether the charts are produced manually or by computer.