Quality and Process Methods • V-Mask CUSUM Control Charts • Overview of V-Mask CUSUM Control Charts
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Overview of V-Mask CUSUM Control Charts
V-Mask 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 less effective at spotting smaller changes, such as a one sigma shift.
Another form of a cumulative sum control chart is the tabular CUSUM chart. To create a tabular CUSUM chart, see CUSUM Control Charts topic. The tabular CUSUM chart is recommended over the V-mask chart for a variety of reasons, including the following:
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The V-mask must be moved with each observation, not simply placed on the last observation.
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The cumulative sums in the V-mask procedure can end up a long way from the center of the graph, even for an on-target process.
Caution: Montgomery (2013) strongly “advises against using the V-mask procedure.”

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Help created on 7/12/2018