Assumptions and Constraint Log

In Lean Six Sigma (LSS), an Assumptions and Constraint Log is a structured tool used during the Define phase of DMAIC to capture factors that may influence the project’s scope, execution, and outcomes. It ensures transparency, helps manage risks, and keeps the team aligned on what is known, assumed, or restricted.

📄 Purpose of the Assumptions & Constraint Log

• Assumptions: Statements believed to be true without full proof (e.g., “Data will be available from the ERP system”).

• Constraints: Limitations that restrict the project (e.g., “Budget capped at $50,000” or “Process changes must not affect regulatory compliance”).

• Why it matters:

  • Prevents surprises later in the project.

  • Provides context for decision-making.

  • Helps identify risks if assumptions prove false.

  • Ensures stakeholders understand boundaries.

⚡ How It Fits into DMAIC

• Define: Document assumptions and constraints early to set realistic scope.

• Measure: Validate assumptions with data (e.g., check accuracy of measurement systems).

• Analyze: Reassess assumptions if root causes differ from expectations.

• Improve: Ensure solutions respect constraints (budget, compliance, timeline).

• Control: Monitor ongoing assumptions (e.g., stable demand) and constraints (e.g., regulatory limits).

🔑 Takeaway

The Assumptions and Constraint Log is a risk management and alignment tool. It ensures Lean Six Sigma projects remain grounded in reality, while highlighting areas that need validation or careful monitoring.