Why: Capability is a component of the effectiveness equation and usually under the control of production.
When: Data for this metric is frequently produced by the Accounting department each month as a segment of the financial reports for the purpose of handling variances against the standards.
Where: Frequently in the effectiveness measure it is a weak point [as a measure of how well the production process des the job for which it was purchased] requiring substantial improvement that cannot be solved by the usual reliability and maintainability (RAM) tools. However, this metric may be deficient from the original design [an issue of design effectiveness] of the system or from the way the system is operated [an issue of use effectiveness].
These definitions are written by H. Paul Barringer and are also posted on his web site at www.barringer1.com