The math is emotionally correct
Years ago, I got into a spirited discussion with a colleague about a quality measurement he wanted each production unit to use within all of our manufacturing sites. He wanted a single performance measure that could be trended over time that showed a production unit’s ability to produce a quality product the very first time. He proposed that we would sum into a single value our already derived individual percentages of rejects, rework, and reallocation of our produced product