At maturity level 4, acquirers establish quantitative objectives for quality and process performance and use them as criteria in managing processes. Quantitative objectives are based on needs of the customer, end users, organization, and process implementers. Quality and process performance is understood in statistical terms and is managed throughout the life of processes.

For selected subprocesses, specific measures of process performance are collected and statistically analyzed. When selecting processes or subprocesses for analyses, it is critical to understand the relationships between different processes and subprocesses and their impact on the acquirer’s and supplier’s performance relative to delivering the product specified by the customer. Such an approach helps to ensure that quantitative and statistical management is applied to where it has the most overall value to the business. Supplier process performance is analyzed as it interfaces with acquirer processes, through data and measures submitted by the supplier. Performance models are used to set performance objectives for both acquirer and supplier performance and to help both parties achieve their objectives.

A critical distinction between maturity levels 3 and 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 typically only qualitatively predictable.