In this paper several control charts for monitoring the variance of a process without subgrouping are analyzed and compared. The comparison in two situations is presented:* When the process mean is assumed to be known and equal to a standard value.* When the value of the process mean is unknown.The following performances are considered:* A moving range chart.* A cumulative sum (CUSUM) chart based on moving ranges.* A CUSUM chart based on an approximate normalizing transformation.* A self-starting CUSUM chart.* A change-point CUSUM chart.* An exponentially weighted moving average chart based on the subgroup variance.
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