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Individuals Control Chart

A control chart that can be used with individual values.  Most control charts require multiple observations per time period and are based on the average, range or standard deviation of these values.  These types of control charts cannot be used with financial data, inventory turns, loss times accidents, number of complaints and many other types of data where only a single value per time period is available.  An individuals control chart must be used for these types of data.

An individuals chart can also be performed on calculated values like the average and range.  This means an individuals control chart can be used for any type of data.  However, with calculated values like the average and standard deviation, control charts specifically designed for such values are generally more powerful and thus preferred.

Control charts are best suited for detecting abnormal points.  They are not nearly as powerful as a change-point analysis in detecting trends.  While a change-point analysis is better at detecting patterns, it fails to detects isolated abnormal points called outliers.  The best approach is to do both.  The change-point analysis determines the broader trends while an accompanying individuals control helps to further isolate abnormal points.