ABSTRACT
If there is a logical rational such as time of day, shift, and so on, for grouping these individual data points into batches, then the equations shown below can be used to calculate the control limits that are used
VCL = X + E2R
CCL = X
LCL = X - E2R
for plotting the individual data points. The constant E2 is shown in Table 4.3 for different sizes of groups. If logical groups do not exist then the same equations can still be employed, but the variation (moving range) between points must be used to generate the r(i) values used to calculate the control lines. If a moving range of size 2 (difference in adjacent points) is utilized then the constant E2 that is obtained from Table 4.3 for the control limit calculation is 2.66.
