Creating a Xbar-R / S control chart

Plot a Shewhart control chart for data collected in rational subgroups to determine if a process is in a state of statistical control.

1. Select a cell in the dataset.
2. On the Analyse-it ribbon tab, in the Statistical Analyses group, click Process Control, and then click the type of control chart:

   Option	Description
   Xbar-R	Plot Shewhart control charts of the mean and range of subgroups.
   Xbar-S	Plot Shewhart control charts of the mean and standard deviation of subgroups.
   Xbar	Plot a Shewhart control chart of the mean of subgroups.
   R	Plot a Shewhart control chart of the range of subgroups.
   S	Plot a Shewhart control chart of the standard deviation of subgroups.

   The analysis task pane opens.
3. In the Process drop-down list, select the quality characteristic variable.
4. In the Sample size group:
   • If the subgroups are identified by a variable, select Subgroup by identifier variable, and in the Id drop-down list, select the subgroup identifier variable.
   • If the subgroups are a constant size and formed by consecutive number of observations of the process variable, select Subgroup size constant, and in the edit box, enter the number of consecutive observations per subgroup.
5. In the Control limits drop-down list:
   • To define control limits based on a multiple of the process sigma, select Sigma, and then in the edit box, type the multiple of the process sigma to define the control limits.
   • To define control limits based on the probability distribution, select Probability, and then in the edit box, type the probability that a single statistic exceeds the control limits, assuming the process is in control.
6. Optional: To specify known process parameters, select the Known process parameters check box, and then in either or both the Mean and Standard deviation edit boxes, type the known value of the parameter.
7. Optional: To show the process mean and sigma statistics, select the Show process statistics check box.
8. Optional: To show the center and control limit statistics, select the Show process control statistics check box.
9. Click Calculate.