1. Appropriate Scale:
The scale should be selected in such a way that the natural variation of the process can be viewed easily.
2. Upper Control Limit (UCL) and 4. Lower Control Limit (LCL):
The ability to determine outliers which signals special causes the control chart requires control limit based on the sampling distribution.
4. Center line:
The control chart requires a centerline based on the sampling distribution in order to allow the determination of non-random patterns which signal special causes.
5. Subgroup Sequence / Timeline:
Maintaining the sequence in which the data are collected provides indications of 'when' a special cause occurs and whether the special cause is time-oriented.
6. Identification of out-of-control plotted values:
Plotted points which are out of statistical control should be identified on the control chart.
7. Event log:
Besides the collection, Charting and analysis of data, additional supporting information should be collected. the information should include any potential sources of variation as well as any action taken to resolve out-of-control signals. When there has not been any change in the process between subgroups, it is not necessary to include an entry on the event log.
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