Six Sigma Green Belt

Answer: C - Unit to department is not a source of variation in robust product design.

Key Takeaway: Robust product design aims to reduce variation in a process without eliminating it. Sources of internal variation can be due to wear and tear of equipment or aging/expiration of materials used. External variation can be due to environmental conditions such as humidity or parasitic infestation. Unit to unit variation can be due to differences in machines and processes.