graph). Note that you don't need to calculate a
value for the lower control limit (LCL R) on the range graph, because for
subgroup sizes up to 6, the LCL R will always be 0.The next part of your calculation sheet covers the calculations for
UCL R (the upper control limit for the range graph), and 3s (3 sigma,
a value which will be used later when calculating the control limits
for the graph). Note that you don't need to calculate a
value for the lower control limit (LCL R) on the range graph, because for
subgroup sizes up to 6, the LCL R will always be 0.
The calculation for UCL R involves multiplying the mean range by the appropriate value of the control chart constant D4. The various control chart constants used in control limit calculations have different values, depending on the size of the subgroups used. The values for D4 for subgroups up to size 5 are given in the bottom right of your calculation sheet. From the printed chart, you will see that the size of the subgroups in this example is 5, so the appropriate value of D4 is 2.114. This value has already been entered into the first box below, and the mean range we have just calculated has been entered into the second box.
Complete the calculation and enter the result into the box outlined in red below. Once again, the result will be one of the control lines on the chart, so it should be rounded to 1 decimal place (i.e. 1 more decimal place than the plotted values). When you have done this, click the button to check your answer.