Performance is Capability
Performance Measurement is the science of establishing quantitatively, the operating performance of a system or process. It may be the efficiency of natural gas processing, the error rate in a cellular phone manufacturing line, the time to process parking tickets or the effectiveness of social service delivery. It doesn’t matter the type of process. If it’s a process, its performance can be measured.
Performance is measured in terms of capability and capability has two components:
(i) location of process performance. Usually this is expressed as the average of process performance. For example, average diameter of a manufactured part is 7.35 centimeters, average time for an EMS vehicle to reach an injured person is 7.3 minutes or a service error rate of 6.39%.
(ii) variation in process performance. This concerns the reliability of the process, the amount of variation it displays. EMS vehicles don’t reach injured persons in 7.3 minutes each and every time. Sometimes less, sometimes more. The level of reliability is usually expressed in units of sigma (the same sigma that gives Six Sigma its name) and/or the coefficient of variation.
If you don’t have a measure for both process location and variation, you don’t have capability and, therefore, don’t have a performance measure. Mixed up statistical nonsense combining standards with measurement, such as measuring the proportion of EMS units arriving within 7.5 minutes, is not encompassing (i) location and (ii) variation. It’s masquerading location as variation and, therefore, a form of evidence corruption.