Six Sigma vs. SPC - How is the 'old' six sigma different from the 'new' six sigma?


Greg Mack

Hi everyone,
I have been reading and learning about six sigma all over the place. Many years ago, I learnt about SPC and the concepts and tools behind it and have used it extensively in my previous employment. Back then, we targeted a cpk of 1.33.
I know that a cpk of 2 is equal to 6 sigma, so therefore, using the "old" SPC approach, if I set goals in my company to achieve 6 sigma through this approach, how is that different from the "new" 6 Sigma methodologies?
This topic has been very frustrating to learn about, as everyone wants to talk about the two, but to me they seem one in the same. It is like "Six Sigma" is the new buzz word for some very old, tried and true methodologies. I would really appreciate someone explaining the difference to me, or providing their own opinions. Thanks for your time.
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Al Dyer


I've been through the training, read the books and consider six sigma a new method for people (consultants/trainers etc...) to make (take) money. What will they think of next when they run out of six sigma customers?

If there is a well defined project management process (based on continuous improvement and preventive action) in place, with total management buy-in, there is no need allocate all those resources and change the direction of a company.

Let's stick to (and improve) the plan and keep it simple!

In my cynical opinion.


Posted before

Rick Goodson


As usual you have a gift for understatement. Maybe the next 'thing' is the same customers at nine sigma. I wish it had been my luck to think up this money making scheme.

Kevin Mader

One of THE Original Covers!

Well said. Honestly, the principles that we follow aren't difficult to understand, just difficult to apply. It takes commitment!



Al Dyer


I agree, application is the hard part and goes along with determination. It does not only apply to work but to everyday life as well. (so much for my pontification)


Ken K.

I agree with most everything mentioned so far. The tools/methods are relatively simple. The execution and acceptance is hard.

Many tend to think of SPC as being primarily for control of industrial processes, but of course it can be applied to just about any process. Also some limit SPC to assessment and control of those processes - not the continous improvement of the processes.

The Six Sigma idea is one of continuous improvement, driven by top management, in ALL areas of your business, not just the product or process that make the product. The idea is to identify areas of the business that need improvement, and use the broad array of "Six Sigma" tools/methods to facilitate/ quantify/maintain those improvments.

If you're using the broadest definition of SPC, then by all means I agree that there is not much new in the land of Six Sigma.

Probably the biggest difference is the idea that SPC is typically a bottom up activity, whereas, Six Sigma tends to be a top down activity. Six Sigma tends to have the direct attention of top level management - SPC typically doesn't.


Originally posted by Al Dyer:
If there is a well defined project management process (based on continuous improvement and preventive action) in place, with total management buy-in, there is no need allocate all those resources and change the direction of a company.

Let's stick to (and improve) the plan and keep it simple!

In my opinion, I view six sigma philosophy a “reactive” quality measure. If it was done right the first time (ie well defined project management process), there would be no need for a six sigma improvement “task force”.

I could only wish that companies would spend half the effort on implementing programs correctly to begin with as they do with spending time putting out fires (with six sigma) on poorly implemented programs.

I don’t deny that six sigma works and is effective. In the same token, six sigma isn’t new. It is the same old quality practices neatly presented in a new wrapper that says “NEW AND IMPROVED”. But in my observations, most companies that are choosing to jump on the in six sigma bandwagon need to put out fires, improve quality and raise the bottom line. In my opinion, six sigma is only part of the solution, the quality systems that allowed the company get into that position to begin with needs to go under the spotlight.

Steven Truchon

Just a slightly different perspective here.

I agree with all that you all have stated in this thread. Six Sigma is yet another name on the same box of cereal.
Our company was "forced" into the Six Sigma arena because one of our primary customers demanded certain cost reductions from all of their suppliers. The statistical tools they provided in the training they supplied has enabled us to isolate production inefficiencies in our processes which when improved has led to cost reductions. They got their percentage cut, and we ended up making more profit. We didnt approach this from a reaction to quality angle, although our PPM's dropped as a result too. Our quality was acceptable by our customers and our standards, but the process efficiency improvements were something I have never read or heard about in any conversation related to Six Sigma or any other "package name".



I beleive 6 Sigma is SPC with a Project Management structure applied to it. (Some companies add a large Hammer) I attended one 6 Sigma conference and came away with the opinion that the consultants are feeding at the trough. Each presenter had their own acronym for the same process. We have been trying to change the culture in our company with Deming 'consultants'that gave us little more than a cheer and a big bill.
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