About PPB and PPMs (Process Performance Baselines and Process Performance Models)

Important to process improvement frameworks (such as CMMI) and to most modern organizations is the ability to measure and detect deviations to common well known (official) process performance baselines (PPB).
Better yet is the capability of "predicting the future" i.e. the behavior of  the process, having as inputs some well known data, supported by the process performance model (PPM).

CMMI-DEV OPP Process Area is intimately related with these concepts (PPB and PPMs) and need them in place for the organizations and its software development process(es) to be be certified.

One example of a process performance model is the COCOMO model, which aims to estimate project cost having as inputs some of the project characteristics:
https://en.wikipedia.org/wiki/COCOMO

Estimation Process and related artifacts

Your QMS could include a process on estimation (that presents the estimation techniques and the associated activities to be executed in order to produce the final estimation sheets that are input for ROMs, Proposals, Change Requests, ...).

One example (INTERNAL):

• https://quality.critical.pt/qmsunified/SUP-support/SUP-09-estimation/CSW-QMS-2010-PCS-00878-estimation-process.pdf#search=sum%20up%20xls

Some common artifacts include templates and models to help you estimating (INTERNAL, use the QMS Portal with the doc id enclosed in double quotes):

• Estimation form (template): CSW-QMS-2011-TPL-02102-estimation-sum-up.xls (now a xltx)
• Planning Poker form (template): CSW-QMS-2015-TPL-02398-planning-poker-estimation.xltx
• Effort Per Phase Model: CSW-QMS-2009-DOC-04974-effort-model-2014-baseline-data4all.xlsx
• Safety Critical Estimation Model: CSW-QMS-2014-DOC-01296-asd-estimation-model.xlsx
• Estimation @ CRITICAL Software - Study on the Estimation Process for CRITICAL Software Projects: CSW-ESTIMATE-2009-PCS-00707-estimation-process.doc

PS. If you're interested in estimation models, google for them. They are very dependent on the business you're working on although there are some attempts to generalize them. 

Example: COCOMO Estimation Model.