ABSTRACT
Chapter 9 introduces the technique of cusum charts for detecting change and shows how cusum charts should be used and interpreted. It also demonstrates the use of cusum charts in product screening and selection and covers briefly the decision procedures for use with cusum charts, including V-masks.
Cusum charts are obtained by determining the difference between the values of individual observations and a ‘target’ value, and cumulating these differences to give a cusum score which is then plotted. The cusum technique can be used for attributes and variables by predetermining the scale for plotting the cusum scores, choosing the target value and setting up a key of slopes corresponding to predetermined changes.
Various decision procedures for the interpretation of cusum plots are possible including the use of V-masks and the design of these is explained.
