Users with engineer privileges can specify default preferences for all capability
analyses.

Select Analysis
Preferences
in the Engineering portal, then navigate to capability
analysis settings. ###### Note

These preferences are the initial settings for all capability analyses. To change settings by measure, go to Specify capability settings for each measure.

- Estimation method for within-subgroup standard deviation (subgroup size > 1)
- Select a method to estimate the
within–subgroup standard deviation when the subgroup size is larger than
1.
- Pooled standard deviation: The pooled standard deviation is the weighted average of subgroup variances, which gives larger subgroups more influence on the overall estimate. This method provides the most precise estimate of standard deviation when the process is in control.
- Rbar: Rbar is the average of the subgroup ranges. This method is a common estimate of the standard deviation and works best with subgroup sizes from 2 to 8.
- Sbar: Sbar is the average of the subgroup standard deviations. This method provides a more precise estimate of the standard deviation than Rbar, especially with subgroup sizes > 8.

- Estimation method for within-subgroup standard deviation (subgroup size = 1)
- Select a method to estimate the within–subgroup standard deviation when
the subgroup size equals 1.
- Average moving range: The average moving range is the average value of the moving range of two or more consecutive points. This method is commonly used when the subgroup size is 1.
- Median moving range: The median moving range is the median value of the moving range of two or more consecutive points. This method is best to use when data have extreme ranges that could influence the moving range.
- Square root of MSSD: The square root of MSSD is the square root of the mean of the squared differences between consecutive points. Use this method when you cannot reasonably assume that at least 2 consecutive points were collected under similar conditions.

- Length of moving range
- Enter the number of observations used to calculate the moving range. The length must be ≤ 100. The default length is 2 because consecutive values have the greatest chance of being alike.

- Use unbiasing constants
- Unbiasing constants reduce the bias that can occur when a parameter is
estimated from a small number of observations. As the number of
observations increases, unbiasing constants have less effect on the
calculated results.
###### Note

Often, the choice to use unbiasing constants depends on company policy or industry standards.

- Estimation method for within-subgroup standard deviation
- Select a method to estimate the within–subgroup standard deviation.
- Pooled standard deviation: The pooled standard deviation is the weighted average of subgroup variances, which gives larger subgroups more influence on the overall estimate. This method provides the most precise estimate of standard deviation when the process is in control.
- Rbar: Rbar is the average of the subgroup ranges. This method is a common estimate of the standard deviation and works best with subgroup sizes from 2 to 8.
- Sbar: Sbar is the average of the subgroup standard deviations. This method provides a more precise estimate of the standard deviation than Rbar, especially with subgroup sizes > 8.

- Estimation method for between-subgroup standard deviation
- Select a method to estimate the between–subgroup standard deviation.
- Average moving range: The average moving range is the average value of the moving range of two or more consecutive points. This method is commonly used when the subgroup size is 1.
- Median moving range: The median moving range is the median value of the moving range of two or more consecutive points. This method is best to use when data have extreme ranges that could influence the moving range.
- Square root of MSSD: The square root of MSSD is the square root of the mean of the squared differences between consecutive points. Use this method when you cannot reasonably assume that at least 2 consecutive points were collected under similar conditions.

- Length of moving range
- Enter the number of observations used to calculate the moving range. The length must be ≤ 100. The default length is 2 because consecutive values have the greatest chance of being alike.

- Use unbiasing constants
- Unbiasing constants reduce the bias that can occur when a parameter is
estimated from a small number of observations. As the number of
observations increases, unbiasing constants have less effect on the
calculated results.
###### Note

Often, the choice to use unbiasing constants depends on company policy or industry standards.