Lean Six Sigma Metrics
Six Sigma metrics focus on any of three, or combination of three, of the following critical factors: cost, quality, and schedule.
You will at times see reference to other CTx metrics, such as Critical to Safety, or Critical to Process. These may be useful, or may be better classified in terms of Cost, Quality and Schedule, which serve as the root drivers for an organization.
In all cases, estimates of processes must consider the stability of the process. See also: Is Your Process Performing?
Critical to Quality (CTQ) Metrics
There are a number of ways to measure process and operational performance, such as the classic Process Capability Indices. An analogous Sigma Level can also be obtained for a given process. Operationally, a Sigma Level that looks across multiple processes in an attempt to show an overall defect rate fro the organization is often fraught with errors.
Critical to Schedule (CTS) Metrics
Critical to Schedule metrics are related to cycle time and scheduling efficiencies, including:
Overall Equipment Effectiveness: combines the notion of CTS and CTQ metrics.
Critical to Cost (CTC) Metrics
Metrics that are determined to be Critical to Quality and Critical to Schedule are (by definition) often Critical to Cost as well. Costs associated with the process issues must include the effect of losses due to Hidden Factory and Customer impact, such as delays in shipments or in information exchange.
Metrics used in CTC evaluations, often to quantify and compare opportunities, include the Net Present Value calculations and Internal Rate of Return calculations