You may choose which methods to use when assessing standard deviation for subgrouped and individuals data.
Control limit method – Choose a standard deviation method for calculating control limits. You can choose either Factors (R-Bar / d2) or Sample standard deviation. The Factors method provides the best prediction if your data exhibits more variation within subgroups than between subgroups, while the Sample standard deviation method provides the best prediction if your data exhibits more variation between subgroups than within subgroups.
SD method used for capability indexes – Choose a method for calculating standard deviation for other statistics. You can choose either Factors (R-Bar / d2) or Sample standard deviation. The Factors method provides the best prediction if your data exhibits more variation within subgroups than between subgroups, while the Sample standard deviation method provides the best prediction if your data exhibits more variation between subgroups than within subgroups.
The method you choose will be used to calculate the Mean +/- 3SD, Mean +/- 4SD, 6SD, Zl, Zu, and Cpm for data in a normal distribution.
If you selected Analysis Mode 2 on Chart Wizard Step 1, one more option is available:
To apply the standard deviation selections to all part numbers or Short Run process specifications that you selected on Chart Wizard Step 1, select the Apply to all items in selected values list check box.
To apply the standard deviation selections only to the values you selected on Chart Wizard Step 3 for retrieval and statistical options, clear the Apply to all items in selected values list check box.
After setting the options on this step, you have several options:
To keep your changes and return to Chart Wizard Step 3, click Finish.
To keep your changes and return to Statistical Options Wizard Step 1, click Back.
To undo your changes and return to Chart Wizard Step 3, click Cancel.
To select which options to use for data that is normally and non-normally distributed, click Next to move to Statistical Options Wizard Step 3.