Improvement Insights Blog

Is Lean Six Sigma stuck in last century thinking? Maybe we just can’t see it. Here’s what I discovered recently.

“I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“Recently, I discovered something and it got me thinking. Now, if you know anything about calculating formulas for an XbarR chart, you know that what you do is if you have some numbers like a subgroup, maybe they got 3.3 and 3.4 or something like that, what you do is calculate for this subgroup what’s the average of the X’s. Well, in this case it’d be 3.3. And then you’d keep doing that for everything underneath there. Then you want to calculate X double bar, which is the average of all of the averages here. So you would take and you would work off of this column to average that column. All right? Get it?

“This is how it was done, but I want you to think that this was done this way for a reason: Because we used to have to do it manually. What you wanted to do was reduce the complexity of the calculation so we would average this to get that, and then we could average this to get that number, whatever that number might have been. Let’s say that was 3.32 or something for the center line of your control chart.

“Now it turns out that maybe you have other things where you only have… you don’t have three samples per subgroup, you only have a subgroup, so you’re supposed to use what’s called a weighted X bar. So instead of this thing, you would then calculate this times 3, and this one would also be 3.3 times 2 to get these sums, and then you would average the weighted sum to get an X double bar. That seems like a lot of work, doesn’t it? But what are we trying to do? We’re trying to manually do this.

“Now the funny thing about this (and you can verify this for yourself), if you come out and just simply run an average like an Excel average of all of the X’s, so if you average all of the X’s, you’ll get exactly the same thing for X double bar, whether it has consistent subgroup sizes or varying subgroup sizes.

“Now what I want you to take away from this is that the way we have always done things may be an artifact of the last century where we had to do everything manually. You know, originally it was probably done with pen and paper, and then we had some sort of calculating machine, and then we had calculators, but now we have spreadsheets to do more advanced things.

“So this got me thinking: We’ve got these artifacts, these formulas for the X bar and weighted X bar and all kinds of things, that are simply artifacts of the last century and how we used to do it. This got me thinking, “What else are the artifacts of the last century?” I think it’s how we taught Lean and Six Sigma like everybody was in manufacturing and they’re not anymore, right? Only about 8% of America works in manufacturing; everybody else works in services and other stuff. So what are we doing? That’s simply carrying on the way things used to be.

“So I don’t think we want to put buggy whips in our Ferraris. I don’t think we should go backwards in time and flog the engine to make it go. I don’t think that’s how it works, right? But this led me to understand that there are things out there that we’ve stopped even thinking about, and there’s often a simpler way to go forward.

“So let’s create a hassle free America, hassle free healthcare. Let’s go out and improve something this week, and let’s do it the simplest way possible.”