Quality improvement people sure love those tools. A particular favorite, of course, is the control chart, of which, I think, seven are usually taught. Two questions I’m always asked are, “Which chart do I use for which situation?” and “When and how often should I recalculate my limits?”

Wrong questions!

Regarding the first (we’ll deal with second question in part 2), I’ve seen many flowcharts in books to help you determine which chart to use for which situation. I find them far too confusing for the average user. (They even give me sweaty palms.) I don’t even teach this in my work.

As my respected colleague Donald Wheeler likes to say, “The purpose is not to have charts. The purpose is to use the charts…. You get no credit for computing the right number—only for taking the right action. Without the follow-through of taking the right action, the computation of the right number is meaningless.”

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