As a Six Sigma Black Belt who is also certified in Lean, I often feel like I am switching languages… or pulling from different toolboxes… when approaching a problem.
I like both methodologies and see benefits in both — but they are certainly not the same.
I say (to anyone who will listen!) that Lean is like your everyday box of household implements: screwdriver, duct tape, flashlight, hammer and nail. It’s inexpensive, easy to use, and gets the job done most of the time.
Six Sigma is your chainsaw: more expensive, more powerful, and only really necessary when the everyday tools don’t work on the problem you’re trying to solve.
(Possibly dangerous in the wrong hands but let’s put a pin in that for now!)
Because it has a high barrier to entry with lots of upfront training and coaching required, and the statistical tools are often complex, Six Sigma makes the most sense in mature improvement environments when most of the ‘low-hanging fruit’ is gone.
If the answers don’t jump out of the data at you, or don’t readily come out of a conversation with your process experts (i.e. your front line team members) then that’s when heavier equipment is needed.
Otherwise give me Lean tools all day long: simple, effective, to the point.