Looking at Six Sigma again, Arturo, looks like it should be applicable to all "systems", accounting, engineering, selling, servicing, even cooking and councelling!
As I said, more a way of observing and thinking - one more step in the history of people revamping old ideas to try to make money out of them. I still have a copy of Edward de Bono's "Lateral Thinking" from the late 60s. They say he invented "lateral thinking" but I would say that he merely attached a catchy name to something that people have done since we started thinking. There is often more than one way to look at things and not all solutions are logical at first sight - intuition, hunches, oddball mental associations etc. are very important.
My favourite word, "serendipity" - the fortuitous accident - has often also been beneficial. But you have to be able to spot the fortuosity, the serendipity, in the first place. Not just cuss 'cos you broke the damn thing again and chuck it in the bin!