In this exercise, we are actually using a specialisation of the XmR chart, often called a Deviation from Aim Chart. This type of chart is used when you want to monitor how far away each sample value is from its target value. The X value recorded on the chart is the difference between the actual value and the target value. The chart is plotted in exactly the same way as a standard XmR chart, but the data recording area has extra boxes where the sample values and the targets can be recorded. This preserves more information about the process than if only the calculated X values were to be recorded.
The required headings have been added to the recording boxes:
The remaining areas on the chart are used to record any additional remarks and for calculating the control limits for the graphs. Calculating control limits is beyond the scope of this course, so you needn't worry about this section.