30 likes | 128 Views
Individuals Chart. Due to High Costs (e.g., destructive testing/measurement) or a lack of data gathering opportunities there may be only one measurement possible in a subgroup. As a rule of thumb, individuals charts should not be used with less than 100 observations. Control limits:.
E N D
Individuals Chart • Due to High Costs (e.g., destructive testing/measurement) or a lack of data gathering opportunities there may be only one measurement possible in a subgroup. As a rule of thumb, individuals charts should not be used with less than 100 observations. • Control limits:
Potential Problems With Individuals Charts • Correlation in the moving range • Need to be conservative in applying rules 2-5 in the moving range charts. • Since the moving ranges are estimates of process variation, inflated control limits can result if the process variation is not stable throughout the sample. • As a rule of thumb, if 2/3 or more of the moving ranges fall below the centerline, inflated control limits use the median of the moving range values instead of the average in calculating control limits