Introduction to Cumulative Sum Charts

Abstract

Conventional charting techniques, such as the Shewhart control charts, described in Chapter 5, have the feature that although points are plotted in time, any testing done on them does not take previous values into account. A technique developed in the late 1950s, however, attempts to include information contained in past data points in order to comment on current performance. This is done, not by looking at the individual data point, but by studying their cumulative sums or ‘cusum’.