According to the PMBOK® Guide (6th Edition), the Estimate Costs process is the process of developing an approximation of the monetary resources needed to complete project work. To create an accurate estimate, the project manager must pull information from various foundational sources.
The inputs for the Estimate Costs process include:
Project Management Plan: Specifically the Cost Management Plan, Quality Management Plan, and Scope Baseline (which includes the Project Scope Statement, WBS, and WBS Dictionary).
Project Documents: This is a broad category including the Lessons Learned Register, Project Schedule, Resource Requirements, and Risk Register.
Enterprise Environmental Factors (EEFs): These include market conditions, published commercial information (like price lists), and exchange rates.
Organizational Process Assets (OPAs): These include cost estimating policies, cost estimating templates, and historical information from previous similar projects.
Analysis of Distractors:
A (Work performance data): This is an input for Monitoring and Controlling processes (like Control Costs). It represents raw observations and measurements identified during activities. It is not used to estimate costs, but rather to compare actual costs against the estimates.
C (Cost baseline / Benefits management plan): The Cost Baseline is an output of the Determine Budget process. It cannot be an input to Estimate Costs because estimating must happen before the baseline is established. The Benefits Management Plan is generally an input to the business side (Initiating/Planning) rather than activity-level cost estimation.
D (Basis of estimates): This is an output of the Estimate Costs process. It provides the supporting detail for how the cost estimates were derived (e.g., how risks were considered, what range of precision was used).
