Creating the Moving Range chart

The next step is to create the moving range chart.

Figure 12.2

The moving range chart (mR chart) will help us to detect if any of the trials are significantly different than the others.

Creating limits for the mR chart

 As with the running record, we will have to first determine the normal variation. To determine the normal variation on the my chart, we must compute the upper range limit (URL).

The formula to calculate the upper range limit is:

URL = 3.27 x mR-Avg

From Table 12.3, we see that the moving range average (mR-Avg) is equal to 42.70. Therefore the URL = 3.27 x 42.70 = 139.63.

Let's now include the URL and the mR-Avg on our mR chart.

In Figure 12.3, the red line is the mR-Avg and the blue line is URL.

 © 2009 Norman Wattenberger