CUSUM Control Chart Overview
Cumulative Sum (CUSUM) control charts show cumulative sums of subgroup or individual measurements from a target value. CUSUM charts can help you decide whether a process is in a state of statistical control by detecting small, sustained shifts in the process mean. In comparison, Shewhart charts can detect sudden and large changes in measurement, such as a two or three sigma shift, but they are ineffective at spotting smaller changes, such as a one sigma shift.
Example of a CUSUM Chart
A machine fills 8-ounce cans of two-cycle engine oil additive. The filling process is believed to be in statistical control. The process is set so that the average weight of a filled can (μ0) is 8.10 ounces. Previous analysis shows ...