Quality of estimate (Cost, Duration, risk, resources, etc.,) is the foundation for successful project or program or portfolio value delivery. SIPOC is one such visual tool or techniques which can be used to improve the accuracy of estimates.

SPIOC model is flowchart tool to perform quality management. Here is an example of how a project manager uses a SIPOC diagram for a simple process, such as “Improve quality of estimates”. The diagram can be created rather quickly by drawing a chart with five columns. Each column is labeled, from left to right, with the letters SIPOC or the words suppliers, inputs, processes, outputs and customers.

In SIPOC charts you start from the center column, process. The process column is kept simple; ideally it lists each step consists of an action and a subject (verb/noun).
Improve quality of estimates
Supplier Input Process Output Customer
Person who going to work on the task Scope Invite Supplier Cost Estimates Project Manager
Consultants OPA (Organization Process Assets) Provide Input Schedule Estimates Project Team
SMEs EEF (Enterprise Environmental factor) Perform Brainstorming Resource estimates
Risk Register Perform Delphi techniques
Stakeholder register Nominal group techniques