As you all know, the influence of W. Edwards Deming on my career and thinking has been profound. A criticism always leveled at him was that he was short on specifics—but he would always growl at someone who alluded to this, “Examples without theory teach nothing!”

Enter Joseph Juran, the other quality giant of the 20th century. When I worked at 3M during the 1980s, they had several sets of his 16-video Juran on Quality Improvement series. I studied it hard and watched several tapes many, many times. He had a good empirical sense (and sense of humor), and having been around the block once or twice, a lot of wisdom. So, let’s apply some of that wisdom to the two scenarios from part one of this three-part series.

Juran always advised as a first strategy: “Exhaust in-house data.” An initial chart analyzing your process is important before doing this. Here’s a key principle of common cause analysis that almost everyone overlooks: The data from any common cause period on a control chart can be aggregated to attempt a “stratification” and apply Juran’s beloved Pareto Principle.

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