In my last three posts I showed you how I look at shop floors, starting with some general guidance (FOCUS!) and going into detail through the different aspects of what I try to observe on the shop floor (5S, visual management, waste, unevenness, overburden, and safety). This usually gives me a reasonable overview of what is going on on the shop floor. However, this is not all I do. For projects, I may have project specific observations (e.g., when I do a SMED project, I observe in detail the actual changeover). But beyond that, there is another source: the available data! Hence, this post will compare information you observed yourself on the shop floor (the gemba) vs. data obtained by others or by computers.