A Box-Cox transformation of your process data can help correct the following conditions:
- The process data are not normally distributed, especially if the data are not collected in subgroups. For more information, go to Normality assumptions for control charts.
- Subgroup variance is unstable because the variation in the data is proportional to the subgroup mean.
You can also perform a Box-Cox transformation when you create a control chart. For example, to transform the data when you create an Xbar-R chart, choose
Where to find this command
To perform a Box-Cox transformation, choose .