Level 4

At maturity level 4, an organization has achieved all the specific goals of the process areas assigned

to maturity levels 2, 3, and 4 and the generic goals assigned to maturity levels 2 and 3. Subprocesses

are selected that significantly contribute to overall process performance. These selected subprocesses

are controlled using statistical and other quantitative techniques.

Quantitative objectives for quality and process performance are established and used as criteria in

managing processes. Quantitative objectives are based on the needs of the customer, end users,

organization, and process implementers. Quality and process performance are understood in statistical

terms and are managed throughout the life of the processes.

For these processes, detailed measures of process performance are collected and statistically

analyzed. Special causes of process variation2 are identified and, where appropriate, the sources of

special causes are corrected to prevent future occurrences.

Quality and process performance measures are incorporated into the organization’s measurement

repository to support fact-based decision making in the future.

A critical distinction between maturity level 3 and maturity level 4 is the predictability of process

performance. At maturity level 4, the performance of processes is controlled using statistical and other

quantitative techniques, and is quantitatively predictable. At maturity level 3, processes are only

qualitatively predictable.