XmR is a moving range chart. It is used when only samples of size one are available. The moving range statistic is
The control limits are computed using
Where 
is the mean of the
observations, 
is the mean of the
moving ranges and is 
is the mean of the
distribution of the ranges of n samples from the normal distribution with
mean of zero and standard deviation of one.
XmR Example
The viscosity of aircraft primer paint was measured. Since the paint is produced in batches, only single samples are available (Montgomery 251).
import com.imsl.chart.*;
import com.imsl.chart.qc.*;
public class SampleXmR extends JFrameChart {
static final double viscosity[] = {
33.75, 33.05, 34.00, 33.81, 33.46, 34.02, 33.68,
33.27, 33.49, 33.20, 33.62, 33.00, 33.54, 33.12, 33.84
};
public SampleXmR() {
Chart chart = getChart();
AxisXY axis = new AxisXY(chart);
XmR xmr = new XmR(axis, viscosity);
}
public static void main(String argv[]) {
new SampleXmR().setVisible(true);
}
}
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