An X-Bar chart displays the averages of a dataset. The average of each subgroup is calculated and plotted as a point on the line chart. This data is shown centered around the blue dotted line, X Double Bar (an average of the averages). Upper and lower control limits are also displayed.
An X-Bar chart is useful for seeing how trends are developing and to see how close to the nominal the average is. This is helpful information when re-calibrating a machine for instance.
Use the Zones checkbox to display colored zones that identify how far each datapoint is from the target value (note that the target value is different from X Double Bar)..
The zones work as follows:
0-1 sigma from target value
1-2 sigma from target value
>2 sigma from target value
These sigma values are used to calculate whether or not a system is in control according to Nelson rules or WECO rules.
Moving the mouse along the chart will display the value and subgroup at that point..
