Quality Advisor

A free online reference for statistical process control, process capability analysis, measurement systems analysis, and control chart interpretation, and other quality metrics.

Capability analysis: Indices

What are the measures of process capability ?

These indices show what the process is "capable" of doing. This is the six sigma range of the inherent variation of a statistically stable process . Sigma is estimated using the /d2 formula.

What are the measures of process performance ?

These indices show what a process is actually doing. This is the six sigma range of the total process variation, where sigma is usually determined by the sample standard deviation .

All of these capability indices can be calculated using software packages like SQCpack.

See also:
>> Can a process produce output within specifications?
>> Control vs capability
>> Normal data capability analysis
>> Non-normal data capability analysis
>> What is capability analysis and when is it used?
>> Learning more about capability