# Statistics Glossary

## Attributes Data

Qualitative data that can be counted for recording and analysis. Examples include characteristics where the results are recorded in a simple yes/no fashion, such as acceptability of a hole diameter when measured with a go/no-go gage, or the presence of a

## Average

The sum of the values divided by the number of values (sample size). It is designated by a bar over the symbol for the values being averaged. This is called X-Bar.

X-Bar is the average of the X values within a subgroup.
X-Double Bar is the average of the subgroup averages.

Basic Statistical Methods

Applies the theory of variation through the use of basic problem-solving techniques and statistical process control. It includes control chart construction and interpretation (for both variables and attributes data) and capability analysis.

Capability

When the process average plus and minus the 3 sigma spread of the distribution of individuals is contained within the specification tolerance

(variables data), or when at least 99.73% of the individuals are within specification (attributes data) and capability analysis. Note that this can be determined only after the process is in statistical control.

Center Line

The line on a control chart that represents the average or median value of the items being plotted (process average).

X = X-Bar = Average of the Subgroup Values

X = X-Double Bar = Average of the Subgroup Averages