Cumulative Sum (CuSum) Chart

In this chart, instead of plotting individual observations, a running sum of the deviations of the individual measurements from the center line or specification is drawn. This chart is particularly powerful in detecting small drift: While in a standard X chart such drift may not generate an out-of-control condition over a large number of samples, the CuSum chart is very sensitive in this respect and will quickly detect such small changes.

Note that STATISTICA computes the recommended tabular or algorithmic CuSum chart, and not the "old-style" V-mask control limits that were commonly in use when these charts were (literally) made by hand. See Montgomery (1996, Chapter 7) for details and recommendations.

For information on how CuSum charts and their control limits are calculated, see QCC Computational Details. See also, Common Types of Charts and Control Chart for Individual Observations,and Multivariate Cumulative Sum Chart.