Moving XBar chart
properties | Configuring a Moving XBar
chart | Moving
XBar chart calculations

Standard XBar control charts are relatively insensitive to small
shifts in the process mean. Control charts based on moving averages
are very effective in detecting small process shifts. Moving
averages are generally used to smooth out the noise in a time
series and forecast future values in a series.

In the following Moving XBar chart example, each plotted point
represents a running average of the subgroup. For example, the
2^{nd} point is the average of the
first 2 points; the 3^{rd} point is an
average of the first 3 points, and so forth. The moving length is
the limit for the number of subgroups used to calculate the
average. In the following example, the moving average is set at 8,
meaning that subgroups are averaged with the 8 consecutive
subgroups preceding and including the plotted subgroup. The control
limits (LCL and UCL) are also dependent on the moving length
setting. In this example, control limits vary for the first 7
subgroups shown. From the 8^{th}
subgroup on, the control limits for all subgroups are constant. The
center line (CL) is the average of all subgroup averages.

### See Also