Defining Six Sigma

Defining Six Sigma

“Shall we continue?” I didn’t want to overwhelm Sid. “Sure,” he replied. “But remember I have a staff meeting at 10.”

For the next hour, I explained to Sid that, regardless of the various window dressings consulting companies hang on Six Sigma, it revolves around a basic problem-solving equation, Y = (f) x or Y = (f) x1 + x2 + x3 . . . . This equation defines the relationship between a dependent variable, Y, and independent variables, the x’s.

Y = (f) x is the basic equation for life. You can be sure of the output only if you can control the inputs.

In other words, the output of a process is a function of the inputs. You know it’s just like your mother used to tell you when you were growing up—you’ll get out of it exactly what you put into it .… This simple problem-solving equation serves as a guide for the Six Sigma methodology of MAIC.

M: Measure

A: Analyze

I: Improve

C: Control

During the Measure phase, the project focus is the Y. Various tools—such as process mapping, basic statistics, capability studies, and measurement system analysis—are used to define and quantify the

project. Besides applying the statistical tools, we also write a problem statement and a project objective and we form a team. At this time the financial impact of the problem and the potential solution to the problem are assessed. Also, members of the company’s financial community must assist and concur with the assessment.

When the Measure phase is completed, we move on to the Analyze phase. Following the problem-solving equation, during this phase we begin to identify the various x’s that are causing the Y to

behave in an unacceptable manner. As we identify the various x’s, hypothesis testing is used to either verify or disprove the various theories and assumptions the team has developed around the causal systems affecting the Y.

Then, after the Analysis phase comes the Improve phase. During this phase, regression analysis and Design of Experiments are used to identify the relationships among the x’s. The x’s are the independent variables in terms of the Y, but that does not mean they’re independent of each other. Variables such as temperature and pressure affect each other and the interaction of the two also affects the Y. We can never completely understand the effect of an interaction without the use of Design of Experiments.

It is the complete understanding of the x’s that allows us to arrive at an optimized solution to the problem at the end of the Improve phase.

Now that we have a solution to the problem, we move to the Control phase to institutionalize the solution. During this phase, quality tools such as mistake proofing, quality systems, and control charts are leveraged to make sure that the problem is eliminated for good.

After explaining these basics of MAIC, I glanced at my watch. It was almost 10 o’clock, so I stopped.

Sid thanked me for my time and left for his meeting. Confident that he now better understood the basics of Six Sigma, I returned to the factory to continue where I had left off the day before.

In retrospect, I’ve been around management long enough that I should have realized it would not be quite that simple.

Although it was a short walk back to the factory, I had barely arrived when Celia called to say that my presence was requested immediately in the executive conference room.

I hung up the phone and started back over toward the conference room.

Key Points

Y = (f)x: Y is the output, the final product. The output is a function of the inputs (the x’s). Only by controlling the inputs can you completely control the output.

Six Sigma methodology:

• M: Measure

• A: Analyze

• I: Improve

• C: Control