# Configuring SPC Parameters

1. Select a controller in the Plant Structure workspace and then select Statistics in the menu bar.

2. In the Configuration section, enter the following parameters to specify how to select tightening results for the statistical calculations:

   Variable Configuration
   Information | Description
   --- | ---
   Number of Subgroups | The number of subgroups the statistical calculation is based upon.
   Subgroup Size | The number of samples (tightening results) in each subgroup. The Subgroup Size can range from 2 through 25.
   Frequency | The interval between the subgroups. Frequency must be equal to or higher than Subgroup Size.

   The total number of results (Number of Subgroups × Frequency) can range from 2 through 500.

   For instance, if Frequency is 8 and Subgroup Size is 5, the first 5 data (results) is used for the subgroup. Because of the Frequency =8, the next subgroup starts considering data (results) from the 8th one on, and so on in a loop.