Welcome to the third installment of our series on lean and Six Sigma. As we saw in the first article, lean and Six Sigma are complementary continuous improvement methodologies that reduce the overall waste and variability, respectively, in production processes. The second article went into some depth on a few of the key principles, tools, and methodologies in lean. Here we conclude our series with a high-level discussion of Six Sigma.

There are many tools in the Six Sigma toolkit—failure mode and effects analysis (FMEA), input-process-output (IPO) diagrams, confidence intervals, histograms, Pareto charts, F-tests, design for Six Sigma (DFSS), and others—that will not be discussed here. The focus here is to discuss the statistical realities that make Six Sigma effective.

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