It's simple. You give the same equipment to two different groups of people, and after a while they're going to have different production levels, different operating costs, and different levels of quality.
這道理很簡單，同樣一套機器設備，交給兩組不同的人去做，經過一段時間以後，你看他們會不會有一樣的產量、品質或成本？