Let’s assume that graphs above present the performance of two different teams in the same company. The black line is an external metric shared with the management, the blue one is observed internally. The black lines are exactly the same so both teams were able to reduce errors significantly to the same level – the goal was achieved. One may say that there is no difference between these two teams. For sure the difference is not observable for a management. Project was finished successfully so we are waiting for a next challenges.