I would describe the difference between the two as one being a “Macro” , the other a “Micro”, and the difference between the two a matter of “control”. If a TV factory has 5 bad TV’s in an eight hour shift, this might be macro information but does not include any details. It not useful for comparing efficiencies. One department may only be able to experience one type of failure and rework the 5 bad TV’s. Their DPM might be 5 PPM if a million TV’s were made. The next department may install several components and the possible number of failures may be a multiple of the series of components, or if the elctronic components are in parallel circuits, or the failures could be inter-related or combinations of failures, the rework may be double, times five, or based on the probability of component failure combinations. The failures (and required rework) may be many times the level of the previous department based on the “Defects per million opportunities)… and yet only 5 TV’s are involved. To compare the efficiencies throughout the company and to know whether quality is getting better or worse department by department, you need the DPMO information for tracking and contolling the efficiency, or quality ouput, (including the amount of waste and rework, of each department.
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