ABSTRACT
Chapter 7 shows how different types of data, including infrequent data, can be analysed using SPC techniques. It describes in detail charts for individuals (run charts) with moving range charts and examines other types of control systems, including zone control and pre-control. The chapter also introduces alternative charts for central tendency: median, mid-range and multi-vari charts; and spread: standard deviation.
It describes the setting up and use of moving mean, moving range and exponentially weighted moving average charts for infrequent data, while outlining some techniques for short run SPC.
When considering the many different types of control charts and processes, charts should be selected for their ease of detecting change, ease of understanding and ability to improve processes. With naturally grouped or past data, conventional mean and range charts should be used. For one-at-a-time data, individual (or run) charts, moving mean/moving range charts and EWMA charts may be more appropriate.
