Defect Definition Table

A Defect Definition Table (DDT) is a Lean Six Sigma tool used during the Measure phase of DMAIC to clearly define what constitutes a defect in a process. It ensures that everyone on the project team has a consistent, objective understanding of what is being measured, which is critical for accurate data collection and analysis.

📄 Purpose

  • Standardization: Prevents ambiguity by clearly stating what counts as a defect.

  • Consistency: Ensures all team members and data collectors classify defects the same way.

  • Accuracy: Improves reliability of defect data, which drives valid analysis.

  • Focus: Helps teams prioritize which defects matter most to customers (Critical to Quality).

✅ Value in LSS Projects

  • Provides clarity for data collection plans.

  • Ensures valid baseline metrics (defects per unit, DPMO, sigma level).

  • Builds credibility with stakeholders by showing objective definitions.

  • Supports root cause analysis by categorizing defects consistently.

🔧 When to Use

  • During Measure phase to define what data will be collected.

  • When multiple teams are involved in defect identification.

  • In processes where “defect” could be interpreted differently by different people.

Takeaway: A Defect Definition Table is the dictionary of defects for your project—it ensures everyone speaks the same language when measuring quality.