Chart Preparation Exercise (2)

As with the other chart types, we will also be using a simple calculation sheet which allows us to take a step-by-step approach to the calculation of control limits. You should print out a copy of the calculation sheet as well.

During the exercise, you will be asked to calculate each of the values on the sheet. Some of the results may need to be rounded to a particular number of decimal places. If this is the case, then you will explicity be told how many places to round the answer to. The general principles covering when to round are basically as follows:

• The value of the mean and the control limits are conventionally rounded to one more decimal place than the values plotted on the graph. In this case, the u values are calculated to 3 decimal places, so the mean and control limits should be rounded to 4 decimal places.
• Intermediate results, which are for use in later calculations should not be rounded (or not as much as the final values).